Eugene Kliuchnikov | 04de756 | 2017-04-13 20:05:36 +0200 | [diff] [blame] | 1 | // Copyright 2016 Google Inc. All Rights Reserved. |
| 2 | // |
| 3 | // Distributed under MIT license. |
| 4 | // See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
| 5 | |
| 6 | // Package cbrotli compresses and decompresses data with C-Brotli library. |
| 7 | package cbrotli |
| 8 | |
| 9 | /* |
| 10 | #include <stddef.h> |
| 11 | #include <stdint.h> |
| 12 | |
| 13 | #include <brotli/decode.h> |
| 14 | |
| 15 | static BrotliDecoderResult DecompressStream(BrotliDecoderState* s, |
| 16 | uint8_t* out, size_t out_len, |
| 17 | const uint8_t* in, size_t in_len, |
| 18 | size_t* bytes_written, |
| 19 | size_t* bytes_consumed) { |
| 20 | size_t in_remaining = in_len; |
| 21 | size_t out_remaining = out_len; |
| 22 | BrotliDecoderResult result = BrotliDecoderDecompressStream( |
| 23 | s, &in_remaining, &in, &out_remaining, &out, NULL); |
| 24 | *bytes_written = out_len - out_remaining; |
| 25 | *bytes_consumed = in_len - in_remaining; |
| 26 | return result; |
| 27 | } |
| 28 | */ |
| 29 | import "C" |
| 30 | |
| 31 | import ( |
| 32 | "bytes" |
| 33 | "errors" |
| 34 | "io" |
| 35 | "io/ioutil" |
| 36 | ) |
| 37 | |
| 38 | type decodeError C.BrotliDecoderErrorCode |
| 39 | |
| 40 | func (err decodeError) Error() string { |
| 41 | return "cbrotli: " + |
| 42 | C.GoString(C.BrotliDecoderErrorString(C.BrotliDecoderErrorCode(err))) |
| 43 | } |
| 44 | |
| 45 | var errExcessiveInput = errors.New("cbrotli: excessive input") |
| 46 | var errInvalidState = errors.New("cbrotli: invalid state") |
| 47 | var errReaderClosed = errors.New("cbrotli: Reader is closed") |
| 48 | |
| 49 | // Reader implements io.ReadCloser by reading Brotli-encoded data from an |
| 50 | // underlying Reader. |
| 51 | type Reader struct { |
| 52 | src io.Reader |
| 53 | state *C.BrotliDecoderState |
| 54 | buf []byte // scratch space for reading from src |
| 55 | in []byte // current chunk to decode; usually aliases buf |
| 56 | } |
| 57 | |
| 58 | // readBufSize is a "good" buffer size that avoids excessive round-trips |
| 59 | // between C and Go but doesn't waste too much memory on buffering. |
| 60 | // It is arbitrarily chosen to be equal to the constant used in io.Copy. |
| 61 | const readBufSize = 32 * 1024 |
| 62 | |
| 63 | // NewReader initializes new Reader instance. |
| 64 | // Close MUST be called to free resources. |
| 65 | func NewReader(src io.Reader) *Reader { |
| 66 | return &Reader{ |
| 67 | src: src, |
| 68 | state: C.BrotliDecoderCreateInstance(nil, nil, nil), |
| 69 | buf: make([]byte, readBufSize), |
| 70 | } |
| 71 | } |
| 72 | |
| 73 | // Close implements io.Closer. Close MUST be invoked to free native resources. |
| 74 | func (r *Reader) Close() error { |
| 75 | if r.state == nil { |
| 76 | return errReaderClosed |
| 77 | } |
| 78 | // Close despite the state; i.e. there might be some unread decoded data. |
| 79 | C.BrotliDecoderDestroyInstance(r.state) |
| 80 | r.state = nil |
| 81 | return nil |
| 82 | } |
| 83 | |
| 84 | func (r *Reader) Read(p []byte) (n int, err error) { |
| 85 | if int(C.BrotliDecoderHasMoreOutput(r.state)) == 0 && len(r.in) == 0 { |
| 86 | m, readErr := r.src.Read(r.buf) |
| 87 | if m == 0 { |
| 88 | // If readErr is `nil`, we just proxy underlying stream behavior. |
| 89 | return 0, readErr |
| 90 | } |
| 91 | r.in = r.buf[:m] |
| 92 | } |
| 93 | |
| 94 | if len(p) == 0 { |
| 95 | return 0, nil |
| 96 | } |
| 97 | |
Eugene Kliuchnikov | 03739d2 | 2017-05-29 17:55:14 +0200 | [diff] [blame] | 98 | for { |
Eugene Kliuchnikov | 04de756 | 2017-04-13 20:05:36 +0200 | [diff] [blame] | 99 | var written, consumed C.size_t |
| 100 | var data *C.uint8_t |
| 101 | if len(r.in) != 0 { |
| 102 | data = (*C.uint8_t)(&r.in[0]) |
| 103 | } |
| 104 | result := C.DecompressStream(r.state, |
| 105 | (*C.uint8_t)(&p[0]), C.size_t(len(p)), |
| 106 | data, C.size_t(len(r.in)), |
| 107 | &written, &consumed) |
| 108 | r.in = r.in[int(consumed):] |
| 109 | n = int(written) |
| 110 | |
| 111 | switch result { |
| 112 | case C.BROTLI_DECODER_RESULT_SUCCESS: |
| 113 | if len(r.in) > 0 { |
| 114 | return n, errExcessiveInput |
| 115 | } |
| 116 | return n, nil |
| 117 | case C.BROTLI_DECODER_RESULT_ERROR: |
| 118 | return n, decodeError(C.BrotliDecoderGetErrorCode(r.state)) |
| 119 | case C.BROTLI_DECODER_RESULT_NEEDS_MORE_OUTPUT: |
| 120 | if n == 0 { |
| 121 | return 0, io.ErrShortBuffer |
| 122 | } |
| 123 | return n, nil |
| 124 | case C.BROTLI_DECODER_NEEDS_MORE_INPUT: |
| 125 | } |
| 126 | |
| 127 | if len(r.in) != 0 { |
| 128 | return 0, errInvalidState |
| 129 | } |
| 130 | |
Eugene Kliuchnikov | 03739d2 | 2017-05-29 17:55:14 +0200 | [diff] [blame] | 131 | // Calling r.src.Read may block. Don't block if we have data to return. |
| 132 | if n > 0 { |
| 133 | return n, nil |
| 134 | } |
| 135 | |
Eugene Kliuchnikov | 04de756 | 2017-04-13 20:05:36 +0200 | [diff] [blame] | 136 | // Top off the buffer. |
| 137 | encN, err := r.src.Read(r.buf) |
Eugene Kliuchnikov | 03739d2 | 2017-05-29 17:55:14 +0200 | [diff] [blame] | 138 | if encN == 0 { |
Eugene Kliuchnikov | 04de756 | 2017-04-13 20:05:36 +0200 | [diff] [blame] | 139 | // Not enough data to complete decoding. |
| 140 | if err == io.EOF { |
| 141 | return 0, io.ErrUnexpectedEOF |
| 142 | } |
| 143 | return 0, err |
| 144 | } |
| 145 | r.in = r.buf[:encN] |
| 146 | } |
| 147 | |
| 148 | return n, nil |
| 149 | } |
| 150 | |
| 151 | // Decode decodes Brotli encoded data. |
| 152 | func Decode(encodedData []byte) ([]byte, error) { |
| 153 | r := &Reader{ |
| 154 | src: bytes.NewReader(nil), |
| 155 | state: C.BrotliDecoderCreateInstance(nil, nil, nil), |
| 156 | buf: make([]byte, 4), // arbitrarily small but nonzero so that r.src.Read returns io.EOF |
| 157 | in: encodedData, |
| 158 | } |
| 159 | defer r.Close() |
| 160 | return ioutil.ReadAll(r) |
| 161 | } |