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 98 for { 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 } 130 131 // Calling r.src.Read may block. Don't block if we have data to return. 132 if n > 0 { 133 return n, nil 134 } 135 136 // Top off the buffer. 137 encN, err := r.src.Read(r.buf) 138 if encN == 0 { 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 } 162
