lib/mime.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/

#include "curl_setup.h"

#include <curl/curl.h>

#include "mime.h"
#include "non-ascii.h"
#include "urldata.h"
#include "sendf.h"

#if !defined(CURL_DISABLE_HTTP) || !defined(CURL_DISABLE_SMTP) || \
    !defined(CURL_DISABLE_IMAP)

#if defined(HAVE_LIBGEN_H) && defined(HAVE_BASENAME)
#include <libgen.h>
#endif

#include "rand.h"
#include "slist.h"
#include "strcase.h"
/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
#include "memdebug.h"

#ifdef WIN32
# ifndef R_OK
#  define R_OK 4
# endif
#endif


#define READ_ERROR                      ((size_t) -1)

/* Encoders. */
static size_t encoder_nop_read(char *buffer, size_t size, bool ateof,
                                curl_mimepart *part);
static curl_off_t encoder_nop_size(curl_mimepart *part);
static size_t encoder_7bit_read(char *buffer, size_t size, bool ateof,
                                curl_mimepart *part);
static size_t encoder_base64_read(char *buffer, size_t size, bool ateof,
                                curl_mimepart *part);
static curl_off_t encoder_base64_size(curl_mimepart *part);
static size_t encoder_qp_read(char *buffer, size_t size, bool ateof,
                              curl_mimepart *part);
static curl_off_t encoder_qp_size(curl_mimepart *part);

static const mime_encoder encoders[] = {
  {"binary", encoder_nop_read, encoder_nop_size},
  {"8bit", encoder_nop_read, encoder_nop_size},
  {"7bit", encoder_7bit_read, encoder_nop_size},
  {"base64", encoder_base64_read, encoder_base64_size},
  {"quoted-printable", encoder_qp_read, encoder_qp_size},
  {ZERO_NULL, ZERO_NULL, ZERO_NULL}
};

/* Base64 encoding table */
static const char base64[] =
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/* Quoted-printable character class table.
 *
 * We cannot rely on ctype functions since quoted-printable input data
 * is assumed to be ascii-compatible, even on non-ascii platforms. */
#define QP_OK           1       /* Can be represented by itself. */
#define QP_SP           2       /* Space or tab. */
#define QP_CR           3       /* Carriage return. */
#define QP_LF           4       /* Line-feed. */
static const unsigned char qp_class[] = {
 0,     0,     0,     0,     0,     0,     0,     0,            /* 00 - 07 */
 0,     QP_SP, QP_LF, 0,     0,     QP_CR, 0,     0,            /* 08 - 0F */
 0,     0,     0,     0,     0,     0,     0,     0,            /* 10 - 17 */
 0,     0,     0,     0,     0,     0,     0,     0,            /* 18 - 1F */
 QP_SP, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK,        /* 20 - 27 */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK,        /* 28 - 2F */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK,        /* 30 - 37 */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, 0    , QP_OK, QP_OK,        /* 38 - 3F */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK,        /* 40 - 47 */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK,        /* 48 - 4F */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK,        /* 50 - 57 */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK,        /* 58 - 5F */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK,        /* 60 - 67 */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK,        /* 68 - 6F */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK,        /* 70 - 77 */
 QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, QP_OK, 0,            /* 78 - 7F */
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                /* 80 - 8F */
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                /* 90 - 9F */
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                /* A0 - AF */
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                /* B0 - BF */
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                /* C0 - CF */
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                /* D0 - DF */
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                /* E0 - EF */
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                 /* F0 - FF */
};


/* Binary --> hexadecimal ASCII table. */
static const char aschex[] =
  "\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x41\x42\x43\x44\x45\x46";



#ifndef __VMS
#define filesize(name, stat_data) (stat_data.st_size)
#define fopen_read fopen

#else

#include <fabdef.h>
/*
 * get_vms_file_size does what it takes to get the real size of the file
 *
 * For fixed files, find out the size of the EOF block and adjust.
 *
 * For all others, have to read the entire file in, discarding the contents.
 * Most posted text files will be small, and binary files like zlib archives
 * and CD/DVD images should be either a STREAM_LF format or a fixed format.
 *
 */
curl_off_t VmsRealFileSize(const char *name,
                           const struct_stat *stat_buf)
{
  char buffer[8192];
  curl_off_t count;
  int ret_stat;
  FILE * file;

  file = fopen(name, FOPEN_READTEXT); /* VMS */
  if(file == NULL)
    return 0;

  count = 0;
  ret_stat = 1;
  while(ret_stat > 0) {
    ret_stat = fread(buffer, 1, sizeof(buffer), file);
    if(ret_stat != 0)
      count += ret_stat;
  }
  fclose(file);

  return count;
}

/*
 *
 *  VmsSpecialSize checks to see if the stat st_size can be trusted and
 *  if not to call a routine to get the correct size.
 *
 */
static curl_off_t VmsSpecialSize(const char *name,
                                 const struct_stat *stat_buf)
{
  switch(stat_buf->st_fab_rfm) {
  case FAB$C_VAR:
  case FAB$C_VFC:
    return VmsRealFileSize(name, stat_buf);
    break;
  default:
    return stat_buf->st_size;
  }
}

#define filesize(name, stat_data) VmsSpecialSize(name, &stat_data)

/*
 * vmsfopenread
 *
 * For upload to work as expected on VMS, different optional
 * parameters must be added to the fopen command based on
 * record format of the file.
 *
 */
static FILE * vmsfopenread(const char *file, const char *mode)
{
  struct_stat statbuf;
  int result;

  result = stat(file, &statbuf);

  switch(statbuf.st_fab_rfm) {
  case FAB$C_VAR:
  case FAB$C_VFC:
  case FAB$C_STMCR:
    return fopen(file, FOPEN_READTEXT); /* VMS */
    break;
  default:
    return fopen(file, FOPEN_READTEXT, "rfm=stmlf", "ctx=stm");
  }
}

#define fopen_read vmsfopenread
#endif


#ifndef HAVE_BASENAME
/*
  (Quote from The Open Group Base Specifications Issue 6 IEEE Std 1003.1, 2004
  Edition)

  The basename() function shall take the pathname pointed to by path and
  return a pointer to the final component of the pathname, deleting any
  trailing '/' characters.

  If the string pointed to by path consists entirely of the '/' character,
  basename() shall return a pointer to the string "/". If the string pointed
  to by path is exactly "//", it is implementation-defined whether '/' or "//"
  is returned.

  If path is a null pointer or points to an empty string, basename() shall
  return a pointer to the string ".".

  The basename() function may modify the string pointed to by path, and may
  return a pointer to static storage that may then be overwritten by a
  subsequent call to basename().

  The basename() function need not be reentrant. A function that is not
  required to be reentrant is not required to be thread-safe.

*/
static char *Curl_basename(char *path)
{
  /* Ignore all the details above for now and make a quick and simple
     implementation here */
  char *s1;
  char *s2;

  s1 = strrchr(path, '/');
  s2 = strrchr(path, '\\');

  if(s1 && s2) {
    path = (s1 > s2? s1 : s2) + 1;
  }
  else if(s1)
    path = s1 + 1;
  else if(s2)
    path = s2 + 1;

  return path;
}

#define basename(x)  Curl_basename((x))
#endif


/* Set readback state. */
static void mimesetstate(mime_state *state, enum mimestate tok, void *ptr)
{
  state->state = tok;
  state->ptr = ptr;
  state->offset = 0;
}


/* Escape header string into allocated memory. */
static char *escape_string(const char *src)
{
  size_t bytecount = 0;
  size_t i;
  char *dst;

  for(i = 0; src[i]; i++)
    if(src[i] == '"' || src[i] == '\\')
      bytecount++;

  bytecount += i;
  dst = malloc(bytecount + 1);
  if(!dst)
    return NULL;

  for(i = 0; *src; src++) {
    if(*src == '"' || *src == '\\')
      dst[i++] = '\\';
    dst[i++] = *src;
  }

  dst[i] = '\0';
  return dst;
}

/* Check if header matches. */
static char *match_header(struct curl_slist *hdr, const char *lbl, size_t len)
{
  char *value = NULL;

  if(strncasecompare(hdr->data, lbl, len) && hdr->data[len] == ':')
    for(value = hdr->data + len + 1; *value == ' '; value++)
      ;
  return value;
}

/* Get a header from an slist. */
static char *search_header(struct curl_slist *hdrlist, const char *hdr)
{
  size_t len = strlen(hdr);
  char *value = NULL;

  for(; !value && hdrlist; hdrlist = hdrlist->next)
    value = match_header(hdrlist, hdr, len);

  return value;
}

static char *strippath(const char *fullfile)
{
  char *filename;
  char *base;
  filename = strdup(fullfile); /* duplicate since basename() may ruin the
                                  buffer it works on */
  if(!filename)
    return NULL;
  base = strdup(basename(filename));

  free(filename); /* free temporary buffer */

  return base; /* returns an allocated string or NULL ! */
}

/* Initialize data encoder state. */
static void cleanup_encoder_state(mime_encoder_state *p)
{
  p->pos = 0;
  p->bufbeg = 0;
  p->bufend = 0;
}


/* Dummy encoder. This is used for 8bit and binary content encodings. */
static size_t encoder_nop_read(char *buffer, size_t size, bool ateof,
                               curl_mimepart *part)
{
  mime_encoder_state *st = &part->encstate;
  size_t insize = st->bufend - st->bufbeg;

  (void) ateof;

  if(size > insize)
    size = insize;
  if(size)
    memcpy(buffer, st->buf, size);
  st->bufbeg += size;
  return size;
}

static curl_off_t encoder_nop_size(curl_mimepart *part)
{
  return part->datasize;
}


/* 7bit encoder: the encoder is just a data validity check. */
static size_t encoder_7bit_read(char *buffer, size_t size, bool ateof,
                                curl_mimepart *part)
{
  mime_encoder_state *st = &part->encstate;
  size_t cursize = st->bufend - st->bufbeg;

  (void) ateof;

  if(size > cursize)
    size = cursize;

  for(cursize = 0; cursize < size; cursize++) {
    *buffer = st->buf[st->bufbeg];
    if(*buffer++ & 0x80)
      return cursize? cursize: READ_ERROR;
    st->bufbeg++;
  }

  return cursize;
}


/* Base64 content encoder. */
static size_t encoder_base64_read(char *buffer, size_t size, bool ateof,
                                curl_mimepart *part)
{
  mime_encoder_state *st = &part->encstate;
  size_t cursize = 0;
  int i;
  char *ptr = buffer;

  while(st->bufbeg < st->bufend) {
    /* Line full ? */
    if(st->pos > MAX_ENCODED_LINE_LENGTH - 4) {
      /* Yes, we need 2 characters for CRLF. */
      if(size < 2)
        break;
      *ptr++ = '\r';
      *ptr++ = '\n';
      st->pos = 0;
      cursize += 2;
      size -= 2;
    }

    /* Be sure there is enough space and input data for a base64 group. */
    if(size < 4 || st->bufend - st->bufbeg < 3)
      break;

    /* Encode three bytes as four characters. */
    i = st->buf[st->bufbeg++] & 0xFF;
    i = (i << 8) | (st->buf[st->bufbeg++] & 0xFF);
    i = (i << 8) | (st->buf[st->bufbeg++] & 0xFF);
    *ptr++ = base64[(i >> 18) & 0x3F];
    *ptr++ = base64[(i >> 12) & 0x3F];
    *ptr++ = base64[(i >> 6) & 0x3F];
    *ptr++ = base64[i & 0x3F];
    cursize += 4;
    st->pos += 4;
    size -= 4;
  }

  /* If at eof, we have to flush the buffered data. */
  if(ateof && size >= 4) {
    /* Buffered data size can only be 0, 1 or 2. */
    ptr[2] = ptr[3] = '=';
    i = 0;
    switch(st->bufend - st->bufbeg) {
    case 2:
      i = (st->buf[st->bufbeg + 1] & 0xFF) << 8;
      /* FALLTHROUGH */
    case 1:
      i |= (st->buf[st->bufbeg] & 0xFF) << 16;
      ptr[0] = base64[(i >> 18) & 0x3F];
      ptr[1] = base64[(i >> 12) & 0x3F];
      if(++st->bufbeg != st->bufend) {
        ptr[2] = base64[(i >> 6) & 0x3F];
        st->bufbeg++;
      }
      cursize += 4;
      st->pos += 4;
      break;
    }
  }

#ifdef CURL_DOES_CONVERSIONS
  /* This is now textual data, Convert character codes. */
  if(part->easy && cursize) {
    CURLcode result = Curl_convert_to_network(part->easy, buffer, cursize);
    if(result)
      return READ_ERROR;
  }
#endif

  return cursize;
}

static curl_off_t encoder_base64_size(curl_mimepart *part)
{
  curl_off_t size = part->datasize;

  if(size <= 0)
    return size;    /* Unknown size or no data. */

  /* Compute base64 character count. */
  size = 4 * (1 + (size - 1) / 3);

  /* Effective character count must include CRLFs. */
  return size + 2 * ((size - 1) / MAX_ENCODED_LINE_LENGTH);
}


/* Quoted-printable lookahead.
 *
 * Check if a CRLF or end of data is in input buffer at current position + n.
 * Return -1 if more data needed, 1 if CRLF or end of data, else 0.
 */
static int qp_lookahead_eol(mime_encoder_state *st, int ateof, size_t n)
{
  n += st->bufbeg;
  if(n >= st->bufend && ateof)
    return 1;
  if(n + 2 > st->bufend)
    return ateof? 0: -1;
  if(qp_class[st->buf[n] & 0xFF] == QP_CR &&
     qp_class[st->buf[n + 1] & 0xFF] == QP_LF)
    return 1;
  return 0;
}

/* Quoted-printable encoder. */
static size_t encoder_qp_read(char *buffer, size_t size, bool ateof,
                              curl_mimepart *part)
{
  mime_encoder_state *st = &part->encstate;
  char *ptr = buffer;
  size_t cursize = 0;
  int i;
  size_t len;
  size_t consumed;
  int softlinebreak;
  char buf[4];

  /* On all platforms, input is supposed to be ASCII compatible: for this
     reason, we use hexadecimal ASCII codes in this function rather than
     character constants that can be interpreted as non-ascii on some
     platforms. Preserve ASCII encoding on output too. */
  while(st->bufbeg < st->bufend) {
    len = 1;
    consumed = 1;
    i = st->buf[st->bufbeg];
    buf[0] = (char) i;
    buf[1] = aschex[(i >> 4) & 0xF];
    buf[2] = aschex[i & 0xF];

    switch(qp_class[st->buf[st->bufbeg] & 0xFF]) {
    case QP_OK:          /* Not a special character. */
      break;
    case QP_SP:          /* Space or tab. */
      /* Spacing must be escaped if followed by CRLF. */
      switch(qp_lookahead_eol(st, ateof, 1)) {
      case -1:          /* More input data needed. */
        return cursize;
      case 0:           /* No encoding needed. */
        break;
      default:          /* CRLF after space or tab. */
        buf[0] = '\x3D';    /* '=' */
        len = 3;
        break;
      }
      break;
    case QP_CR:         /* Carriage return. */
      /* If followed by a line-feed, output the CRLF pair.
         Else escape it. */
      switch(qp_lookahead_eol(st, ateof, 0)) {
      case -1:          /* Need more data. */
        return cursize;
      case 1:           /* CRLF found. */
        buf[len++] = '\x0A';    /* Append '\n'. */
        consumed = 2;
        break;
      default:          /* Not followed by LF: escape. */
        buf[0] = '\x3D';    /* '=' */
        len = 3;
        break;
      }
      break;
    default:            /* Character must be escaped. */
      buf[0] = '\x3D';    /* '=' */
      len = 3;
      break;
    }

    /* Be sure the encoded character fits within maximum line length. */
    if(buf[len - 1] != '\x0A') {    /* '\n' */
      softlinebreak = st->pos + len > MAX_ENCODED_LINE_LENGTH;
      if(!softlinebreak && st->pos + len == MAX_ENCODED_LINE_LENGTH) {
        /* We may use the current line only if end of data or followed by
           a CRLF. */
        switch(qp_lookahead_eol(st, ateof, consumed)) {
        case -1:        /* Need more data. */
          return cursize;
          break;
        case 0:         /* Not followed by a CRLF. */
          softlinebreak = 1;
          break;
        }
      }
      if(softlinebreak) {
        strcpy(buf, "\x3D\x0D\x0A");    /* "=\r\n" */
        len = 3;
        consumed = 0;
      }
    }

    /* If the output buffer would overflow, do not store. */
    if(len > size)
      break;

    /* Append to output buffer. */
    memcpy(ptr, buf, len);
    cursize += len;
    ptr += len;
    size -= len;
    st->pos += len;
    if(buf[len - 1] == '\x0A')    /* '\n' */
      st->pos = 0;
    st->bufbeg += consumed;
  }

  return cursize;
}

static curl_off_t encoder_qp_size(curl_mimepart *part)
{
  /* Determining the size can only be done by reading the data: unless the
     data size is 0, we return it as unknown (-1). */
  return part->datasize? -1: 0;
}


/* In-memory data callbacks. */
/* Argument is a pointer to the mime part. */
static size_t mime_mem_read(char *buffer, size_t size, size_t nitems,
                            void *instream)
{
  curl_mimepart *part = (curl_mimepart *) instream;
  size_t sz = (size_t) part->datasize - part->state.offset;
  (void) size;   /* Always 1.*/

  if(sz > nitems)
    sz = nitems;

  if(sz)
    memcpy(buffer, (char *) &part->data[part->state.offset], sz);

  part->state.offset += sz;
  return sz;
}

static int mime_mem_seek(void *instream, curl_off_t offset, int whence)
{
  curl_mimepart *part = (curl_mimepart *) instream;

  switch(whence) {
  case SEEK_CUR:
    offset += part->state.offset;
    break;
  case SEEK_END:
    offset += part->datasize;
    break;
  }

  if(offset < 0 || offset > part->datasize)
    return CURL_SEEKFUNC_FAIL;

  part->state.offset = (size_t) offset;
  return CURL_SEEKFUNC_OK;
}

static void mime_mem_free(void *ptr)
{
  Curl_safefree(((curl_mimepart *) ptr)->data);
}


/* Named file callbacks. */
/* Argument is a pointer to the mime part. */
static int mime_open_file(curl_mimepart * part)
{
  /* Open a MIMEKIND_FILE part. */

  if(part->fp)
    return 0;
  part->fp = fopen_read(part->data, "rb");
  return part->fp? 0: -1;
}

static size_t mime_file_read(char *buffer, size_t size, size_t nitems,
                             void *instream)
{
  curl_mimepart *part = (curl_mimepart *) instream;

  if(mime_open_file(part))
    return READ_ERROR;

  return fread(buffer, size, nitems, part->fp);
}

static int mime_file_seek(void *instream, curl_off_t offset, int whence)
{
  curl_mimepart *part = (curl_mimepart *) instream;

  if(whence == SEEK_SET && !offset && !part->fp)
    return CURL_SEEKFUNC_OK;   /* Not open: implicitly already at BOF. */

  if(mime_open_file(part))
    return CURL_SEEKFUNC_FAIL;

  return fseek(part->fp, (long) offset, whence)?
               CURL_SEEKFUNC_CANTSEEK: CURL_SEEKFUNC_OK;
}

static void mime_file_free(void *ptr)
{
  curl_mimepart *part = (curl_mimepart *) ptr;

  if(part->fp) {
    fclose(part->fp);
    part->fp = NULL;
  }
  Curl_safefree(part->data);
  part->data = NULL;
}


/* Subparts callbacks. */
/* Argument is a pointer to the mime structure. */

/* Readback a byte string segment. */
static size_t readback_bytes(mime_state *state,
                             char *buffer, size_t bufsize,
                             const char *bytes, size_t numbytes,
                             const char *trail)
{
  size_t sz;

  if(numbytes > state->offset) {
    sz = numbytes - state->offset;
    bytes += state->offset;
  }
  else {
    size_t tsz = strlen(trail);

    sz = state->offset - numbytes;
    if(sz >= tsz)
      return 0;
    bytes = trail + sz;
    sz = tsz - sz;
  }

  if(sz > bufsize)
    sz = bufsize;

  memcpy(buffer, bytes, sz);
  state->offset += sz;
  return sz;
}

/* Read a non-encoded part content. */
static size_t read_part_content(curl_mimepart *part,
                                char *buffer, size_t bufsize)
{
  size_t sz = 0;

  if(part->readfunc)
    sz = part->readfunc(buffer, 1, bufsize, part->arg);
  return sz;
}

/* Read and encode part content. */
static size_t read_encoded_part_content(curl_mimepart *part,
                                        char *buffer, size_t bufsize)
{
  mime_encoder_state *st = &part->encstate;
  size_t cursize = 0;
  size_t sz;
  bool ateof = FALSE;

  while(bufsize) {
    if(st->bufbeg < st->bufend || ateof) {
      /* Encode buffered data. */
      sz = part->encoder->encodefunc(buffer, bufsize, ateof, part);
      switch(sz) {
      case 0:
        if(ateof)
          return cursize;
        break;
      case CURL_READFUNC_ABORT:
      case CURL_READFUNC_PAUSE:
      case READ_ERROR:
        return cursize? cursize: sz;
      default:
        cursize += sz;
        buffer += sz;
        bufsize -= sz;
        continue;
      }
    }

    /* We need more data in input buffer. */
    if(st->bufbeg) {
      size_t len = st->bufend - st->bufbeg;

      if(len)
        memmove(st->buf, st->buf + st->bufbeg, len);
      st->bufbeg = 0;
      st->bufend = len;
    }
    if(st->bufend >= sizeof st->buf)
      return cursize? cursize: READ_ERROR;    /* Buffer full. */
    sz = read_part_content(part, st->buf + st->bufend,
                           sizeof st->buf - st->bufend);
    switch(sz) {
    case 0:
      ateof = TRUE;
      break;
    case CURL_READFUNC_ABORT:
    case CURL_READFUNC_PAUSE:
    case READ_ERROR:
      return cursize? cursize: sz;
    default:
      st->bufend += sz;
      break;
    }
  }

  return cursize;
}

/* Readback a mime part. */
static size_t readback_part(curl_mimepart *part,
                            char *buffer, size_t bufsize)
{
  size_t cursize = 0;
  size_t sz;
  struct curl_slist *hdr;
#ifdef CURL_DOES_CONVERSIONS
  char *convbuf = buffer;
#endif

  /* Readback from part. */

  while(bufsize) {
    sz = 0;
    hdr = (struct curl_slist *) part->state.ptr;
    switch(part->state.state) {
    case MIMESTATE_BEGIN:
      mimesetstate(&part->state, part->flags & MIME_BODY_ONLY? MIMESTATE_BODY:
                                 MIMESTATE_CURLHEADERS, part->curlheaders);
      break;
    case MIMESTATE_USERHEADERS:
      if(!hdr) {
        mimesetstate(&part->state, MIMESTATE_EOH, NULL);
        break;
      }
      if(match_header(hdr, "Content-Type", 12)) {
        mimesetstate(&part->state, MIMESTATE_USERHEADERS, hdr->next);
        break;
      }
      /* FALLTHROUGH */
    case MIMESTATE_CURLHEADERS:
      if(!hdr)
        mimesetstate(&part->state, MIMESTATE_USERHEADERS, part->userheaders);
      else {
        sz = readback_bytes(&part->state, buffer, bufsize,
                            hdr->data, strlen(hdr->data), "\r\n");
        if(!sz)
          mimesetstate(&part->state, part->state.state, hdr->next);
      }
      break;
    case MIMESTATE_EOH:
      sz = readback_bytes(&part->state, buffer, bufsize, "\r\n", 2, "");
      if(!sz)
        mimesetstate(&part->state, MIMESTATE_BODY, NULL);
      break;
    case MIMESTATE_BODY:
#ifdef CURL_DOES_CONVERSIONS
      if(part->easy && convbuf < buffer) {
        CURLcode result = Curl_convert_to_network(part->easy, convbuf,
                                                  buffer - convbuf);
        if(result)
          return READ_ERROR;
        convbuf = buffer;
      }
#endif
      cleanup_encoder_state(&part->encstate);
      mimesetstate(&part->state, MIMESTATE_CONTENT, NULL);
      break;
    case MIMESTATE_CONTENT:
      if(part->encoder)
        sz = read_encoded_part_content(part, buffer, bufsize);
      else
        sz = read_part_content(part, buffer, bufsize);
      switch(sz) {
      case 0:
        mimesetstate(&part->state, MIMESTATE_END, NULL);
        /* Try sparing open file descriptors. */
        if(part->kind == MIMEKIND_FILE && part->fp) {
          fclose(part->fp);
          part->fp = NULL;
        }
        /* FALLTHROUGH */
      case CURL_READFUNC_ABORT:
      case CURL_READFUNC_PAUSE:
      case READ_ERROR:
        return cursize? cursize: sz;
      }
      break;
    case MIMESTATE_END:
      return cursize;
    default:
      break;    /* Other values not in part state. */
    }

    /* Bump buffer and counters according to read size. */
    cursize += sz;
    buffer += sz;
    bufsize -= sz;
  }

#ifdef CURL_DOES_CONVERSIONS
      if(part->easy && convbuf < buffer &&
         part->state.state < MIMESTATE_BODY) {
        CURLcode result = Curl_convert_to_network(part->easy, convbuf,
                                                  buffer - convbuf);
        if(result)
          return READ_ERROR;
      }
#endif

  return cursize;
}

/* Readback from mime. */
static size_t mime_subparts_read(char *buffer, size_t size, size_t nitems,
                                 void *instream)
{
  curl_mime *mime = (curl_mime *) instream;
  size_t cursize = 0;
  size_t sz;
  curl_mimepart *part;
#ifdef CURL_DOES_CONVERSIONS
  char *convbuf = buffer;
#endif

  (void) size;   /* Always 1. */

  while(nitems) {
    sz = 0;
    part = mime->state.ptr;
    switch(mime->state.state) {
    case MIMESTATE_BEGIN:
    case MIMESTATE_BODY:
#ifdef CURL_DOES_CONVERSIONS
      convbuf = buffer;
#endif
      mimesetstate(&mime->state, MIMESTATE_BOUNDARY1, mime->firstpart);
      /* The first boundary always follows the header termination empty line,
         so is always preceded by a CRLK. We can then spare 2 characters
         by skipping the leading CRLF in boundary. */
      mime->state.offset += 2;
      break;
    case MIMESTATE_BOUNDARY1:
      sz = readback_bytes(&mime->state, buffer, nitems, "\r\n--", 4, "");
      if(!sz)
        mimesetstate(&mime->state, MIMESTATE_BOUNDARY2, part);
      break;
    case MIMESTATE_BOUNDARY2:
      sz = readback_bytes(&mime->state, buffer, nitems, mime->boundary,
                          strlen(mime->boundary), part? "\r\n": "--\r\n");
      if(!sz) {
#ifdef CURL_DOES_CONVERSIONS
        if(mime->easy && convbuf < buffer) {
          CURLcode result = Curl_convert_to_network(mime->easy, convbuf,
                                                    buffer - convbuf);
          if(result)
            return READ_ERROR;
          convbuf = buffer;
        }
#endif
        mimesetstate(&mime->state, MIMESTATE_CONTENT, part);
      }
      break;
    case MIMESTATE_CONTENT:
      if(!part) {
        mimesetstate(&mime->state, MIMESTATE_END, NULL);
        break;
      }
      sz = readback_part(part, buffer, nitems);
      switch(sz) {
      case CURL_READFUNC_ABORT:
      case CURL_READFUNC_PAUSE:
      case READ_ERROR:
        return cursize? cursize: sz;
      case 0:
#ifdef CURL_DOES_CONVERSIONS
        convbuf = buffer;
#endif
        mimesetstate(&mime->state, MIMESTATE_BOUNDARY1, part->nextpart);
        break;
      }
      break;
    case MIMESTATE_END:
      return cursize;
    default:
      break;    /* other values not used in mime state. */
    }

    /* Bump buffer and counters according to read size. */
    cursize += sz;
    buffer += sz;
    nitems -= sz;
  }

#ifdef CURL_DOES_CONVERSIONS
      if(mime->easy && convbuf < buffer &&
         mime->state.state <= MIMESTATE_CONTENT) {
        CURLcode result = Curl_convert_to_network(mime->easy, convbuf,
                                                  buffer - convbuf);
        if(result)
          return READ_ERROR;
      }
#endif

  return cursize;
}

static int mime_part_rewind(curl_mimepart *part)
{
  int res = CURL_SEEKFUNC_OK;
  enum mimestate targetstate = MIMESTATE_BEGIN;

  if(part->flags & MIME_BODY_ONLY)
    targetstate = MIMESTATE_BODY;
  cleanup_encoder_state(&part->encstate);
  if(part->state.state > targetstate) {
    res = CURL_SEEKFUNC_CANTSEEK;
    if(part->seekfunc) {
      res = part->seekfunc(part->arg, (curl_off_t) 0, SEEK_SET);
      switch(res) {
      case CURL_SEEKFUNC_OK:
      case CURL_SEEKFUNC_FAIL:
      case CURL_SEEKFUNC_CANTSEEK:
        break;
      case -1:    /* For fseek() error. */
        res = CURL_SEEKFUNC_CANTSEEK;
        break;
      default:
        res = CURL_SEEKFUNC_FAIL;
        break;
      }
    }
  }

  if(res == CURL_SEEKFUNC_OK)
    mimesetstate(&part->state, targetstate, NULL);

  return res;
}

static int mime_subparts_seek(void *instream, curl_off_t offset, int whence)
{
  curl_mime *mime = (curl_mime *) instream;
  curl_mimepart *part;
  int result = CURL_SEEKFUNC_OK;
  int res;

  if(whence != SEEK_SET || offset)
    return CURL_SEEKFUNC_CANTSEEK;    /* Only support full rewind. */

  if(mime->state.state == MIMESTATE_BEGIN)
   return CURL_SEEKFUNC_OK;           /* Already rewound. */

  for(part = mime->firstpart; part; part = part->nextpart) {
    res = mime_part_rewind(part);
    if(res != CURL_SEEKFUNC_OK)
      result = res;
  }

  if(result == CURL_SEEKFUNC_OK)
    mimesetstate(&mime->state, MIMESTATE_BEGIN, NULL);

  return result;
}

/* Release part content. */
static void cleanup_part_content(curl_mimepart *part)
{
  if(part->freefunc)
    part->freefunc(part->arg);

  part->readfunc = NULL;
  part->seekfunc = NULL;
  part->freefunc = NULL;
  part->arg = (void *) part;          /* Defaults to part itself. */
  part->data = NULL;
  part->fp = NULL;
  part->datasize = (curl_off_t) 0;    /* No size yet. */
  cleanup_encoder_state(&part->encstate);
  part->kind = MIMEKIND_NONE;
}

static void mime_subparts_free(void *ptr)
{
  curl_mime *mime = (curl_mime *) ptr;

  if(mime && mime->parent) {
    mime->parent->freefunc = NULL;  /* Be sure we won't be called again. */
    cleanup_part_content(mime->parent);  /* Avoid dangling pointer in part. */
  }
  curl_mime_free(mime);
}

/* Do not free subparts: unbind them. This is used for the top level only. */
static void mime_subparts_unbind(void *ptr)
{
  curl_mime *mime = (curl_mime *) ptr;

  if(mime && mime->parent) {
    mime->parent->freefunc = NULL;  /* Be sure we won't be called again. */
    cleanup_part_content(mime->parent);  /* Avoid dangling pointer in part. */
    mime->parent = NULL;
  }
}


void Curl_mime_cleanpart(curl_mimepart *part)
{
  cleanup_part_content(part);
  curl_slist_free_all(part->curlheaders);
  if(part->flags & MIME_USERHEADERS_OWNER)
    curl_slist_free_all(part->userheaders);
  Curl_safefree(part->mimetype);
  Curl_safefree(part->name);
  Curl_safefree(part->filename);
  Curl_mime_initpart(part, part->easy);
}

/* Recursively delete a mime handle and its parts. */
void curl_mime_free(curl_mime *mime)
{
  curl_mimepart *part;

  if(mime) {
    mime_subparts_unbind(mime);  /* Be sure it's not referenced anymore. */
    while(mime->firstpart) {
      part = mime->firstpart;
      mime->firstpart = part->nextpart;
      Curl_mime_cleanpart(part);
      free(part);
    }

    free(mime->boundary);
    free(mime);
  }
}

CURLcode Curl_mime_duppart(curl_mimepart *dst, const curl_mimepart *src)
{
  curl_mime *mime;
  curl_mimepart *d;
  const curl_mimepart *s;
  CURLcode res = CURLE_OK;

  /* Duplicate content. */
  switch(src->kind) {
  case MIMEKIND_NONE:
    break;
  case MIMEKIND_DATA:
    res = curl_mime_data(dst, src->data, (size_t) src->datasize);
    break;
  case MIMEKIND_FILE:
    res = curl_mime_filedata(dst, src->data);
    /* Do not abort duplication if file is not readable. */
    if(res == CURLE_READ_ERROR)
      res = CURLE_OK;
    break;
  case MIMEKIND_CALLBACK:
    res = curl_mime_data_cb(dst, src->datasize, src->readfunc,
                            src->seekfunc, src->freefunc, src->arg);
    break;
  case MIMEKIND_MULTIPART:
    /* No one knows about the cloned subparts, thus always attach ownership
       to the part. */
    mime = curl_mime_init(dst->easy);
    res = mime? curl_mime_subparts(dst, mime): CURLE_OUT_OF_MEMORY;

    /* Duplicate subparts. */
    for(s = ((curl_mime *) src->arg)->firstpart; !res && s; s = s->nextpart) {
      d = curl_mime_addpart(mime);
      res = d? Curl_mime_duppart(d, s): CURLE_OUT_OF_MEMORY;
    }
    break;
  default:  /* Invalid kind: should not occur. */
    res = CURLE_BAD_FUNCTION_ARGUMENT;  /* Internal error? */
    break;
  }

  /* Duplicate headers. */
  if(!res && src->userheaders) {
    struct curl_slist *hdrs = Curl_slist_duplicate(src->userheaders);

    if(!hdrs)
      res = CURLE_OUT_OF_MEMORY;
    else {
      /* No one but this procedure knows about the new header list,
         so always take ownership. */
      res = curl_mime_headers(dst, hdrs, TRUE);
      if(res)
        curl_slist_free_all(hdrs);
    }
  }

  /* Duplicate other fields. */
  if(dst != NULL)
    dst->encoder = src->encoder;
  else
    res = CURLE_WRITE_ERROR;
  if(!res)
    res = curl_mime_type(dst, src->mimetype);
  if(!res)
    res = curl_mime_name(dst, src->name);
  if(!res)
    res = curl_mime_filename(dst, src->filename);

  /* If an error occurred, rollback. */
  if(res && dst)
    Curl_mime_cleanpart(dst);

  return res;
}

/*
 * Mime build functions.
 */

/* Create a mime handle. */
curl_mime *curl_mime_init(struct Curl_easy *easy)
{
  curl_mime *mime;

  mime = (curl_mime *) malloc(sizeof *mime);

  if(mime) {
    mime->easy = easy;
    mime->parent = NULL;
    mime->firstpart = NULL;
    mime->lastpart = NULL;

    /* Get a part boundary. */
    mime->boundary = malloc(24 + MIME_RAND_BOUNDARY_CHARS + 1);
    if(!mime->boundary) {
      free(mime);
      return NULL;
    }

    memset(mime->boundary, '-', 24);
    Curl_rand_hex(easy, (unsigned char *) mime->boundary + 24,
                  MIME_RAND_BOUNDARY_CHARS + 1);
    mimesetstate(&mime->state, MIMESTATE_BEGIN, NULL);
  }

  return mime;
}

/* Initialize a mime part. */
void Curl_mime_initpart(curl_mimepart *part, struct Curl_easy *easy)
{
  memset((char *) part, 0, sizeof *part);
  part->easy = easy;
  mimesetstate(&part->state, MIMESTATE_BEGIN, NULL);
}

/* Create a mime part and append it to a mime handle's part list. */
curl_mimepart *curl_mime_addpart(curl_mime *mime)
{
  curl_mimepart *part;

  if(!mime)
    return NULL;

  part = (curl_mimepart *) malloc(sizeof *part);

  if(part) {
    Curl_mime_initpart(part, mime->easy);
    part->parent = mime;

    if(mime->lastpart)
      mime->lastpart->nextpart = part;
    else
      mime->firstpart = part;

    mime->lastpart = part;
  }

  return part;
}

/* Set mime part name. */
CURLcode curl_mime_name(curl_mimepart *part, const char *name)
{
  if(!part)
    return CURLE_BAD_FUNCTION_ARGUMENT;

  Curl_safefree(part->name);
  part->name = NULL;

  if(name) {
    part->name = strdup(name);
    if(!part->name)
      return CURLE_OUT_OF_MEMORY;
  }

  return CURLE_OK;
}

/* Set mime part remote file name. */
CURLcode curl_mime_filename(curl_mimepart *part, const char *filename)
{
  if(!part)
    return CURLE_BAD_FUNCTION_ARGUMENT;

  Curl_safefree(part->filename);
  part->filename = NULL;

  if(filename) {
    part->filename = strdup(filename);
    if(!part->filename)
      return CURLE_OUT_OF_MEMORY;
  }

  return CURLE_OK;
}

/* Set mime part content from memory data. */
CURLcode curl_mime_data(curl_mimepart *part,
                        const char *data, size_t datasize)
{
  if(!part)
    return CURLE_BAD_FUNCTION_ARGUMENT;

  cleanup_part_content(part);

  if(data) {
    if(datasize == CURL_ZERO_TERMINATED)
      datasize = strlen(data);

    part->data = malloc(datasize + 1);
    if(!part->data)
      return CURLE_OUT_OF_MEMORY;

    part->datasize = datasize;

    if(datasize)
      memcpy(part->data, data, datasize);
    part->data[datasize] = '\0';    /* Set a nul terminator as sentinel. */

    part->readfunc = mime_mem_read;
    part->seekfunc = mime_mem_seek;
    part->freefunc = mime_mem_free;
    part->kind = MIMEKIND_DATA;
  }

  return CURLE_OK;
}

/* Set mime part content from named local file. */
CURLcode curl_mime_filedata(curl_mimepart *part, const char *filename)
{
  CURLcode result = CURLE_OK;
  char *base;

  if(!part)
    return CURLE_BAD_FUNCTION_ARGUMENT;

  cleanup_part_content(part);

  if(filename) {
    struct_stat sbuf;

    if(stat(filename, &sbuf) || access(filename, R_OK))
      result = CURLE_READ_ERROR;

    part->data = strdup(filename);
    if(!part->data)
      result = CURLE_OUT_OF_MEMORY;

    part->datasize = -1;
    if(!result && S_ISREG(sbuf.st_mode)) {
      part->datasize = filesize(filename, sbuf);
      part->seekfunc = mime_file_seek;
    }

    part->readfunc = mime_file_read;
    part->freefunc = mime_file_free;
    part->kind = MIMEKIND_FILE;

    /* As a side effect, set the filename to the current file's base name.
       It is possible to withdraw this by explicitly calling
       curl_mime_filename() with a NULL filename argument after the current
       call. */
    base = strippath(filename);
    if(!base)
      result = CURLE_OUT_OF_MEMORY;
    else {
      CURLcode res = curl_mime_filename(part, base);

      if(res)
        result = res;
      free(base);
    }
  }
  return result;
}

/* Set mime part type. */
CURLcode curl_mime_type(curl_mimepart *part, const char *mimetype)
{
  if(!part)
    return CURLE_BAD_FUNCTION_ARGUMENT;

  Curl_safefree(part->mimetype);
  part->mimetype = NULL;

  if(mimetype) {
    part->mimetype = strdup(mimetype);
    if(!part->mimetype)
      return CURLE_OUT_OF_MEMORY;
  }

  return CURLE_OK;
}

/* Set mime data transfer encoder. */
CURLcode curl_mime_encoder(curl_mimepart *part, const char *encoding)
{
  CURLcode result = CURLE_BAD_FUNCTION_ARGUMENT;
  const mime_encoder *mep;

  if(!part)
    return result;

  part->encoder = NULL;

  if(!encoding)
    return CURLE_OK;    /* Removing current encoder. */

  for(mep = encoders; mep->name; mep++)
    if(strcasecompare(encoding, mep->name)) {
      part->encoder = mep;
      result = CURLE_OK;
    }

  return result;
}

/* Set mime part headers. */
CURLcode curl_mime_headers(curl_mimepart *part,
                           struct curl_slist *headers, int take_ownership)
{
  if(!part)
    return CURLE_BAD_FUNCTION_ARGUMENT;

  if(part->flags & MIME_USERHEADERS_OWNER) {
    if(part->userheaders != headers)  /* Allow setting twice the same list. */
      curl_slist_free_all(part->userheaders);
    part->flags &= ~MIME_USERHEADERS_OWNER;
  }
  part->userheaders = headers;
  if(headers && take_ownership)
    part->flags |= MIME_USERHEADERS_OWNER;
  return CURLE_OK;
}

/* Set mime part content from callback. */
CURLcode curl_mime_data_cb(curl_mimepart *part, curl_off_t datasize,
                           curl_read_callback readfunc,
                           curl_seek_callback seekfunc,
                           curl_free_callback freefunc, void *arg)
{
  if(!part)
    return CURLE_BAD_FUNCTION_ARGUMENT;

  cleanup_part_content(part);

  if(readfunc) {
    part->readfunc = readfunc;
    part->seekfunc = seekfunc;
    part->freefunc = freefunc;
    part->arg = arg;
    part->datasize = datasize;
    part->kind = MIMEKIND_CALLBACK;
  }

  return CURLE_OK;
}

/* Set mime part content from subparts. */
CURLcode Curl_mime_set_subparts(curl_mimepart *part,
                                curl_mime *subparts, int take_ownership)
{
  curl_mime *root;

  if(!part)
    return CURLE_BAD_FUNCTION_ARGUMENT;

  /* Accept setting twice the same subparts. */
  if(part->kind == MIMEKIND_MULTIPART && part->arg == subparts)
    return CURLE_OK;

  cleanup_part_content(part);

  if(subparts) {
    /* Must belong to the same data handle. */
    if(part->easy && subparts->easy && part->easy != subparts->easy)
      return CURLE_BAD_FUNCTION_ARGUMENT;

    /* Should not have been attached already. */
    if(subparts->parent)
      return CURLE_BAD_FUNCTION_ARGUMENT;

    /* Should not be the part's root. */
    root = part->parent;
    if(root) {
      while(root->parent && root->parent->parent)
        root = root->parent->parent;
      if(subparts == root) {
        if(part->easy)
          failf(part->easy, "Can't add itself as a subpart!");
        return CURLE_BAD_FUNCTION_ARGUMENT;
      }
    }

    subparts->parent = part;
    part->readfunc = mime_subparts_read;
    part->seekfunc = mime_subparts_seek;
    part->freefunc = take_ownership? mime_subparts_free: mime_subparts_unbind;
    part->arg = subparts;
    part->datasize = -1;
    part->kind = MIMEKIND_MULTIPART;
  }

  return CURLE_OK;
}

CURLcode curl_mime_subparts(curl_mimepart *part, curl_mime *subparts)
{
  return Curl_mime_set_subparts(part, subparts, TRUE);
}


/* Readback from top mime. */
/* Argument is the dummy top part. */
size_t Curl_mime_read(char *buffer, size_t size, size_t nitems, void *instream)
{
  curl_mimepart *part = (curl_mimepart *) instream;

  (void) size;   /* Always 1. */
  return readback_part(part, buffer, nitems);
}

/* Rewind mime stream. */
CURLcode Curl_mime_rewind(curl_mimepart *part)
{
  return mime_part_rewind(part) == CURL_SEEKFUNC_OK?
         CURLE_OK: CURLE_SEND_FAIL_REWIND;
}

/* Compute header list size. */
static size_t slist_size(struct curl_slist *s,
                         size_t overhead, const char *skip)
{
  size_t size = 0;
  size_t skiplen = skip? strlen(skip): 0;

  for(; s; s = s->next)
    if(!skip || !match_header(s, skip, skiplen))
      size += strlen(s->data) + overhead;
  return size;
}

/* Get/compute multipart size. */
static curl_off_t multipart_size(curl_mime *mime)
{
  curl_off_t size;
  curl_off_t sz;
  size_t boundarysize;
  curl_mimepart *part;

  if(!mime)
    return 0;           /* Not present -> empty. */

  boundarysize = 4 + strlen(mime->boundary) + 2;
  size = boundarysize;  /* Final boundary - CRLF after headers. */

  for(part = mime->firstpart; part; part = part->nextpart) {
    sz = Curl_mime_size(part);

    if(sz < 0)
      size = sz;

    if(size >= 0)
      size += boundarysize + sz;
  }

  return size;
}

/* Get/compute mime size. */
curl_off_t Curl_mime_size(curl_mimepart *part)
{
  curl_off_t size;

  if(part->kind == MIMEKIND_MULTIPART)
    part->datasize = multipart_size(part->arg);

  size = part->datasize;

  if(part->encoder)
    size = part->encoder->sizefunc(part);

  if(size >= 0 && !(part->flags & MIME_BODY_ONLY)) {
    /* Compute total part size. */
    size += slist_size(part->curlheaders, 2, NULL);
    size += slist_size(part->userheaders, 2, "Content-Type");
    size += 2;    /* CRLF after headers. */
  }
  return size;
}

/* Add a header. */
/* VARARGS2 */
CURLcode Curl_mime_add_header(struct curl_slist **slp, const char *fmt, ...)
{
  struct curl_slist *hdr = NULL;
  char *s = NULL;
  va_list ap;

  va_start(ap, fmt);
  s = curl_mvaprintf(fmt, ap);
  va_end(ap);

  if(s) {
    hdr = Curl_slist_append_nodup(*slp, s);
    if(hdr)
      *slp = hdr;
    else
      free(s);
  }

  return hdr? CURLE_OK: CURLE_OUT_OF_MEMORY;
}

/* Add a content type header. */
static CURLcode add_content_type(struct curl_slist **slp,
                                 const char *type, const char *boundary)
{
  return Curl_mime_add_header(slp, "Content-Type: %s%s%s", type,
                              boundary? "; boundary=": "",
                              boundary? boundary: "");
}

const char *Curl_mime_contenttype(const char *filename)
{
  unsigned int i;

  /*
   * If no content type was specified, we scan through a few well-known
   * extensions and pick the first we match!
   */
  struct ContentType {
    const char *extension;
    const char *type;
  };
  static const struct ContentType ctts[] = {
    {".gif",  "image/gif"},
    {".jpg",  "image/jpeg"},
    {".jpeg", "image/jpeg"},
    {".png",  "image/png"},
    {".svg",  "image/svg+xml"},
    {".txt",  "text/plain"},
    {".htm",  "text/html"},
    {".html", "text/html"},
    {".pdf",  "application/pdf"},
    {".xml",  "application/xml"}
  };

  if(filename) {
    size_t len1 = strlen(filename);
    const char *nameend = filename + len1;

    for(i = 0; i < sizeof ctts / sizeof ctts[0]; i++) {
      size_t len2 = strlen(ctts[i].extension);

      if(len1 >= len2 && strcasecompare(nameend - len2, ctts[i].extension))
          return ctts[i].type;
    }
  }
  return NULL;
}

CURLcode Curl_mime_prepare_headers(curl_mimepart *part,
                                   const char *contenttype,
                                   const char *disposition,
                                   enum mimestrategy strategy)
{
  curl_mime *mime = NULL;
  const char *boundary = NULL;
  char *customct;
  const char *cte = NULL;
  CURLcode ret = CURLE_OK;

  /* Get rid of previously prepared headers. */
  curl_slist_free_all(part->curlheaders);
  part->curlheaders = NULL;

  /* Be sure we won't access old headers later. */
  if(part->state.state == MIMESTATE_CURLHEADERS)
    mimesetstate(&part->state, MIMESTATE_CURLHEADERS, NULL);

  /* Check if content type is specified. */
  customct = part->mimetype;
  if(!customct)
    customct = search_header(part->userheaders, "Content-Type");
  if(customct)
    contenttype = customct;

  /* If content type is not specified, try to determine it. */
  if(!contenttype) {
    switch(part->kind) {
    case MIMEKIND_MULTIPART:
      contenttype = MULTIPART_CONTENTTYPE_DEFAULT;
      break;
    case MIMEKIND_FILE:
      contenttype = Curl_mime_contenttype(part->filename);
      if(!contenttype)
        contenttype = Curl_mime_contenttype(part->data);
      if(!contenttype && part->filename)
        contenttype = FILE_CONTENTTYPE_DEFAULT;
      break;
    default:
      contenttype = Curl_mime_contenttype(part->filename);
      break;
    }
  }

  if(part->kind == MIMEKIND_MULTIPART) {
    mime = (curl_mime *) part->arg;
    if(mime)
      boundary = mime->boundary;
  }
  else if(contenttype && !customct &&
          strcasecompare(contenttype, "text/plain"))
    if(strategy == MIMESTRATEGY_MAIL || !part->filename)
      contenttype = NULL;

  /* Issue content-disposition header only if not already set by caller. */
  if(!search_header(part->userheaders, "Content-Disposition")) {
    if(!disposition)
      if(part->filename || part->name ||
        (contenttype && !strncasecompare(contenttype, "multipart/", 10)))
          disposition = DISPOSITION_DEFAULT;
    if(disposition && curl_strequal(disposition, "attachment") &&
     !part->name && !part->filename)
      disposition = NULL;
    if(disposition) {
      char *name = NULL;
      char *filename = NULL;

      if(part->name) {
        name = escape_string(part->name);
        if(!name)
          ret = CURLE_OUT_OF_MEMORY;
      }
      if(!ret && part->filename) {
        filename = escape_string(part->filename);
        if(!filename)
          ret = CURLE_OUT_OF_MEMORY;
      }
      if(!ret)
        ret = Curl_mime_add_header(&part->curlheaders,
                                   "Content-Disposition: %s%s%s%s%s%s%s",
                                   disposition,
                                   name? "; name=\"": "",
                                   name? name: "",
                                   name? "\"": "",
                                   filename? "; filename=\"": "",
                                   filename? filename: "",
                                   filename? "\"": "");
      Curl_safefree(name);
      Curl_safefree(filename);
      if(ret)
        return ret;
      }
    }

  /* Issue Content-Type header. */
  if(contenttype) {
    ret = add_content_type(&part->curlheaders, contenttype, boundary);
    if(ret)
      return ret;
  }

  /* Content-Transfer-Encoding header. */
  if(!search_header(part->userheaders, "Content-Transfer-Encoding")) {
    if(part->encoder)
      cte = part->encoder->name;
    else if(contenttype && strategy == MIMESTRATEGY_MAIL &&
     part->kind != MIMEKIND_MULTIPART)
      cte = "8bit";
    if(cte) {
      ret = Curl_mime_add_header(&part->curlheaders,
                                 "Content-Transfer-Encoding: %s", cte);
      if(ret)
        return ret;
    }
  }

  /* If we were reading curl-generated headers, restart with new ones (this
     should not occur). */
  if(part->state.state == MIMESTATE_CURLHEADERS)
    mimesetstate(&part->state, MIMESTATE_CURLHEADERS, part->curlheaders);

  /* Process subparts. */
  if(part->kind == MIMEKIND_MULTIPART && mime) {
    curl_mimepart *subpart;

    disposition = NULL;
    if(strcasecompare(contenttype, "multipart/form-data"))
      disposition = "form-data";
    for(subpart = mime->firstpart; subpart; subpart = subpart->nextpart) {
      ret = Curl_mime_prepare_headers(subpart, NULL, disposition, strategy);
      if(ret)
        return ret;
    }
  }
  return ret;
}

#else /* !CURL_DISABLE_HTTP || !CURL_DISABLE_SMTP || !CURL_DISABLE_IMAP */

/* Mime not compiled in: define stubs for externally-referenced functions. */
curl_mime *curl_mime_init(CURL *easy)
{
  (void) easy;
  return NULL;
}

void curl_mime_free(curl_mime *mime)
{
  (void) mime;
}

curl_mimepart *curl_mime_addpart(curl_mime *mime)
{
  (void) mime;
  return NULL;
}

CURLcode curl_mime_name(curl_mimepart *part, const char *name)
{
  (void) part;
  (void) name;
  return CURLE_NOT_BUILT_IN;
}

CURLcode curl_mime_filename(curl_mimepart *part, const char *filename)
{
  (void) part;
  (void) filename;
  return CURLE_NOT_BUILT_IN;
}

CURLcode curl_mime_type(curl_mimepart *part, const char *mimetype)
{
  (void) part;
  (void) mimetype;
  return CURLE_NOT_BUILT_IN;
}

CURLcode curl_mime_encoder(curl_mimepart *part, const char *encoding)
{
  (void) part;
  (void) encoding;
  return CURLE_NOT_BUILT_IN;
}

CURLcode curl_mime_data(curl_mimepart *part,
                        const char *data, size_t datasize)
{
  (void) part;
  (void) data;
  (void) datasize;
  return CURLE_NOT_BUILT_IN;
}

CURLcode curl_mime_filedata(curl_mimepart *part, const char *filename)
{
  (void) part;
  (void) filename;
  return CURLE_NOT_BUILT_IN;
}

CURLcode curl_mime_data_cb(curl_mimepart *part,
                           curl_off_t datasize,
                           curl_read_callback readfunc,
                           curl_seek_callback seekfunc,
                           curl_free_callback freefunc,
                           void *arg)
{
  (void) part;
  (void) datasize;
  (void) readfunc;
  (void) seekfunc;
  (void) freefunc;
  (void) arg;
  return CURLE_NOT_BUILT_IN;
}

CURLcode curl_mime_subparts(curl_mimepart *part, curl_mime *subparts)
{
  (void) part;
  (void) subparts;
  return CURLE_NOT_BUILT_IN;
}

CURLcode curl_mime_headers(curl_mimepart *part,
                           struct curl_slist *headers, int take_ownership)
{
  (void) part;
  (void) headers;
  (void) take_ownership;
  return CURLE_NOT_BUILT_IN;
}

void Curl_mime_initpart(curl_mimepart *part, struct Curl_easy *easy)
{
  (void) part;
  (void) easy;
}

void Curl_mime_cleanpart(curl_mimepart *part)
{
  (void) part;
}

CURLcode Curl_mime_duppart(curl_mimepart *dst, const curl_mimepart *src)
{
  (void) dst;
  (void) src;
  return CURLE_OK;    /* Nothing to duplicate: always succeed. */
}

CURLcode Curl_mime_set_subparts(curl_mimepart *part,
                                curl_mime *subparts, int take_ownership)
{
  (void) part;
  (void) subparts;
  (void) take_ownership;
  return CURLE_NOT_BUILT_IN;
}

CURLcode Curl_mime_prepare_headers(curl_mimepart *part,
                                   const char *contenttype,
                                   const char *disposition,
                                   enum mimestrategy strategy)
{
  (void) part;
  (void) contenttype;
  (void) disposition;
  (void) strategy;
  return CURLE_NOT_BUILT_IN;
}

curl_off_t Curl_mime_size(curl_mimepart *part)
{
  (void) part;
  return (curl_off_t) -1;
}

size_t Curl_mime_read(char *buffer, size_t size, size_t nitems, void *instream)
{
  (void) buffer;
  (void) size;
  (void) nitems;
  (void) instream;
  return 0;
}

CURLcode Curl_mime_rewind(curl_mimepart *part)
{
  (void) part;
  return CURLE_NOT_BUILT_IN;
}

/* VARARGS2 */
CURLcode Curl_mime_add_header(struct curl_slist **slp, const char *fmt, ...)
{
  (void) slp;
  (void) fmt;
  return CURLE_NOT_BUILT_IN;
}

#endif /* !CURL_DISABLE_HTTP || !CURL_DISABLE_SMTP || !CURL_DISABLE_IMAP */