Alex Deymo | a5cff22 | 2015-04-08 14:10:30 -0700 | [diff] [blame^] | 1 | // Copyright 2015 The Chromium OS Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #include "extents.h" |
| 6 | |
Gilad Arnold | 99b5374 | 2013-04-30 09:24:14 -0700 | [diff] [blame] | 7 | #include <assert.h> |
| 8 | #include <errno.h> |
| 9 | #include <limits.h> |
| 10 | #include <stdint.h> |
| 11 | #include <stdlib.h> |
| 12 | |
Gilad Arnold | 99b5374 | 2013-04-30 09:24:14 -0700 | [diff] [blame] | 13 | |
| 14 | #define TRUE 1 |
| 15 | #define FALSE 0 |
| 16 | |
| 17 | /* Minimum/maximum values for arbitrary integer types. */ |
| 18 | #define UNSIGNED_INT_MAX(t) (~((t)0)) |
| 19 | #define SIGNED_INT_MAX(t) ((t)((uintmax_t)UNSIGNED_INT_MAX(t) >> 1)) |
| 20 | #define MAX(a,b) ((a) > (b) ? (a) : (b)) |
| 21 | #define INT_TYPE_MAX(t) MAX(UNSIGNED_INT_MAX(t), SIGNED_INT_MAX(t)) |
| 22 | |
| 23 | /* The maximum accepted value for a given integer type when parsed as a signed |
| 24 | * long long integer. This is defined to be the smaller of the maximum value |
| 25 | * that can be represented by this type and LLONG_MAX. This bound allows us to |
| 26 | * properly check that parsed values do not exceed the capacity of their |
| 27 | * intended store, regardless of how its size relates to that of a signed long |
| 28 | * long integer. Note: this may mean that we are losing the most significant |
| 29 | * bit of an unsigned 64-bit field (e.g. size_t on some platforms), however |
| 30 | * still permitting values up to 2^62, which is more than enough for all |
| 31 | * practical purposes. */ |
| 32 | #define LLONG_MAX_BOUND(s) \ |
| 33 | ((uintmax_t)(s) < (uintmax_t)LLONG_MAX ? (long long)(s) : LLONG_MAX) |
| 34 | #define MAX_ALLOWED(t) LLONG_MAX_BOUND(INT_TYPE_MAX(t)) |
| 35 | |
| 36 | /* Get the type of a struct field. */ |
| 37 | #define FIELD_TYPE(t, f) typeof(((t *)0)->f) |
| 38 | |
| 39 | |
| 40 | /* Reads a long long integer from |s| into |*val_p|. Returns a pointer to the |
| 41 | * character immediately following the specified |delim|, unless (a) parsing |
| 42 | * failed (overflow or no valid digits); (b) the read value is less than |
| 43 | * |min_val| or greater than |max_val|; (c) the delimiter character is not |
| 44 | * |delim|, or the string ends although |may_end| is false. In any of these |
| 45 | * cases, returns NULL. */ |
| 46 | const char * |
| 47 | read_llong(const char *s, long long *val_p, long long min_val, |
| 48 | long long max_val, char delim, int may_end) |
| 49 | { |
| 50 | assert(val_p); |
| 51 | const char *next_s; |
| 52 | errno = 0; |
| 53 | long long val = strtoll(s, (char **)&next_s, 10); |
| 54 | if (((val == LLONG_MAX || val == LLONG_MIN) && errno == ERANGE) || |
| 55 | next_s == s || val < min_val || val > max_val || |
| 56 | (*next_s ? *next_s != delim : !may_end)) |
| 57 | return NULL; /* bad value or delimiter */ |
| 58 | *val_p = val; |
| 59 | if (*next_s) |
| 60 | next_s++; /* skip delimeter */ |
| 61 | return next_s; |
| 62 | } |
| 63 | |
| 64 | |
| 65 | /* Reads a comma-separated list of "offset:length" extents from |ex_str|. If |
| 66 | * |ex_arr| is NULL, then |ex_count| is ignored and it attempts to parse valid |
| 67 | * extents until the end of the string is reached. Otherwise, stores up to |
| 68 | * |ex_count| extents into |ex_arr|, which must be of at least this size. |
| 69 | * Returns the number of correctly parsed extents, or -1 if a malformed extent |
| 70 | * was found. */ |
| 71 | static ssize_t |
| 72 | extents_read(const char *ex_str, ex_t *ex_arr, size_t ex_count) |
| 73 | { |
| 74 | size_t i; |
| 75 | size_t last_i = ex_count - 1; |
| 76 | if (!ex_arr) { |
| 77 | ex_count = SIZE_MAX; |
| 78 | last_i = 0; |
| 79 | } |
| 80 | for (i = 0; *ex_str && i < ex_count; i++) { |
| 81 | long long raw_off = 0, raw_len = 0; |
| 82 | if (!((ex_str = read_llong(ex_str, &raw_off, -1, |
| 83 | MAX_ALLOWED(FIELD_TYPE(ex_t, off)), |
| 84 | ':', FALSE)) && |
| 85 | (ex_str = read_llong(ex_str, &raw_len, 1, |
| 86 | MAX_ALLOWED(FIELD_TYPE(ex_t, len)), |
| 87 | ',', i >= last_i)))) |
| 88 | return -1; /* parsing error */ |
| 89 | if (ex_arr) { |
| 90 | ex_arr[i].off = raw_off; |
| 91 | ex_arr[i].len = raw_len; |
| 92 | } |
| 93 | } |
| 94 | return i; |
| 95 | } |
| 96 | |
| 97 | |
| 98 | ex_t * |
| 99 | extents_parse(const char *ex_str, ex_t *ex_arr, size_t *ex_count_p) |
| 100 | { |
| 101 | /* Sanity checks: a string must be provided; if an array is provided, an |
| 102 | * array count must be given as well. */ |
| 103 | if (!ex_str || (ex_arr && !ex_count_p)) |
| 104 | return NULL; |
| 105 | |
| 106 | /* Parse string and count extents. */ |
| 107 | ssize_t ret = extents_read(ex_str, NULL, 0); |
| 108 | if (ret < 0) |
| 109 | return NULL; /* parsing error */ |
| 110 | size_t ex_count = (size_t)ret; |
| 111 | |
| 112 | /* Input is good, commit to extent count. */ |
| 113 | if (ex_count_p) { |
| 114 | size_t alloc_ex_count = *ex_count_p; |
| 115 | *ex_count_p = ex_count; |
| 116 | if (ex_arr && alloc_ex_count < ex_count) |
| 117 | return NULL; /* insufficient allocated space */ |
| 118 | } |
| 119 | if (ex_count == 0) |
| 120 | return NULL; /* no extents, nothing to do */ |
| 121 | |
| 122 | /* Allocate extent array, if needed. */ |
| 123 | if (!(ex_arr || (ex_arr = (ex_t *)malloc(sizeof(ex_t) * ex_count)))) |
| 124 | return NULL; /* allocation failed */ |
| 125 | |
| 126 | /* Populate the extent array. */ |
| 127 | extents_read(ex_str, ex_arr, ex_count); |
| 128 | |
| 129 | return ex_arr; |
| 130 | } |