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encode.h(3) Library Functions Manual encode.h(3) NAME encode.h - API for Brotli compression. SYNOPSIS Macros #define BROTLI_DEFAULT_MODE BROTLI_MODE_GENERIC Default value for BROTLI_PARAM_MODE parameter. #define BROTLI_DEFAULT_QUALITY 11 Default value for BROTLI_PARAM_QUALITY parameter. #define BROTLI_DEFAULT_WINDOW 22 Default value for BROTLI_PARAM_LGWIN parameter. #define BROTLI_LARGE_MAX_WINDOW_BITS 30 Maximal value for BROTLI_PARAM_LGWIN parameter in 'Large Window Brotli' (32-bit). #define BROTLI_MAX_INPUT_BLOCK_BITS 24 Maximal value for BROTLI_PARAM_LGBLOCK parameter. #define BROTLI_MAX_QUALITY 11 Maximal value for BROTLI_PARAM_QUALITY parameter. #define BROTLI_MAX_WINDOW_BITS 24 Maximal value for BROTLI_PARAM_LGWIN parameter. #define BROTLI_MIN_INPUT_BLOCK_BITS 16 Minimal value for BROTLI_PARAM_LGBLOCK parameter. #define BROTLI_MIN_QUALITY 0 Minimal value for BROTLI_PARAM_QUALITY parameter. #define BROTLI_MIN_WINDOW_BITS 10 Minimal value for BROTLI_PARAM_LGWIN parameter. Typedefs typedef enum BrotliEncoderMode BrotliEncoderMode Options for BROTLI_PARAM_MODE parameter. typedef enum BrotliEncoderOperation BrotliEncoderOperation Operations that can be performed by streaming encoder. typedef enum BrotliEncoderParameter BrotliEncoderParameter Options to be used with BrotliEncoderSetParameter. typedef struct BrotliEncoderStateStruct BrotliEncoderState Opaque structure that holds encoder state. Enumerations Functions BROTLI_BOOL BrotliEncoderAttachPreparedDictionary (BrotliEncoderState *state, const BrotliEncoderPreparedDictionary *dictionary) Attaches a prepared dictionary of any type to the encoder. BROTLI_BOOL BrotliEncoderCompress (int quality, int lgwin, BrotliEncoder- Mode mode, size_t input_size, const uint8_t input_buffer[input_size], size_t *encoded_size, uint8_t encoded_buffer[*encoded_size]) Performs one-shot memory-to-memory compression. BROTLI_BOOL BrotliEncoderCompressStream (BrotliEncoderState *state, BrotliEncoderOperation op, size_t *available_in, const uint8_t **next_in, size_t *available_out, uint8_t **next_out, size_t *to- tal_out) Compresses input stream to output stream. BrotliEncoderState * BrotliEncoderCreateInstance (brotli_alloc_func al- loc_func, brotli_free_func free_func, void *opaque) Creates an instance of BrotliEncoderState and initializes it. void BrotliEncoderDestroyInstance (BrotliEncoderState *state) Deinitializes and frees BrotliEncoderState instance. BROTLI_BOOL BrotliEncoderHasMoreOutput (BrotliEncoderState *state) Checks if encoder has more output. BROTLI_BOOL BrotliEncoderIsFinished (BrotliEncoderState *state) Checks if encoder instance reached the final state. size_t BrotliEncoderMaxCompressedSize (size_t input_size) Calculates the output size bound for the given input_size. BrotliEncoderPreparedDictionary * BrotliEncoderPrepareDictionary (BrotliSharedDictionaryType type, size_t data_size, const uint8_t data[data_size], int quality, brotli_alloc_func alloc_func, brotli_free_func free_func, void *opaque) Prepares a shared dictionary from the given file format for the en- coder. BROTLI_BOOL BrotliEncoderSetParameter (BrotliEncoderState *state, BrotliEn- coderParameter param, uint32_t value) Sets the specified parameter to the given encoder instance. const uint8_t * BrotliEncoderTakeOutput (BrotliEncoderState *state, size_t *size) Acquires pointer to internal output buffer. uint32_t BrotliEncoderVersion (void) Gets an encoder library version. Detailed Description API for Brotli compression. Macro Definition Documentation #define BROTLI_DEFAULT_MODE BROTLI_MODE_GENERIC Default value for BROTLI_PARAM_MODE parameter. #define BROTLI_DEFAULT_QUALITY 11 Default value for BROTLI_PARAM_QUALITY parameter. #define BROTLI_DEFAULT_WINDOW 22 Default value for BROTLI_PARAM_LGWIN parameter. #define BROTLI_MAX_INPUT_BLOCK_BITS 24 Maximal value for BROTLI_PARAM_LGBLOCK parameter. #define BROTLI_MAX_QUALITY 11 Maximal value for BROTLI_PARAM_QUALITY parameter. #define BROTLI_MAX_WINDOW_BITS 24 Maximal value for BROTLI_PARAM_LGWIN parameter. Note: equal to BROTLI_MAX_DISTANCE_BITS constant. #define BROTLI_MIN_INPUT_BLOCK_BITS 16 Minimal value for BROTLI_PARAM_LGBLOCK parameter. #define BROTLI_MIN_QUALITY 0 Minimal value for BROTLI_PARAM_QUALITY parameter. #define BROTLI_MIN_WINDOW_BITS 10 Minimal value for BROTLI_PARAM_LGWIN parameter. Typedef Documentation typedef enum BrotliEncoderMode BrotliEncoderMode Options for BROTLI_PARAM_MODE parameter. typedef enum BrotliEncoderOperation BrotliEncoderOperation Operations that can be performed by streaming encoder. typedef enum BrotliEncoderParameter BrotliEncoderParameter Options to be used with BrotliEncoderSetParameter. typedef struct BrotliEncoderStateStruct BrotliEncoderState Opaque structure that holds encoder state. Allocated and initialized with BrotliEncoderCreateInstance. Cleaned up and deallocated with BrotliEn- coderDestroyInstance. Enumeration Type Documentation enum BrotliEncoderMode Options for BROTLI_PARAM_MODE parameter. Enumerator BROTLI_MODE_GENERIC Default compression mode. In this mode compressor does not know any- thing in advance about the properties of the input. BROTLI_MODE_TEXT Compression mode for UTF-8 formatted text input. BROTLI_MODE_FONT Compression mode used in WOFF 2.0. enum BrotliEncoderOperation Operations that can be performed by streaming encoder. Enumerator BROTLI_OPERATION_PROCESS Process input. Encoder may postpone producing output, until it has processed enough input. BROTLI_OPERATION_FLUSH Produce output for all processed input. Actual flush is performed when input stream is depleted and there is enough space in output stream. This means that client should repeat BROTLI_OPERATION_FLUSH operation until available_in becomes 0, and BrotliEncoderHasMoreOut- put returns BROTLI_FALSE. If output is acquired via BrotliEncoder- TakeOutput, then operation should be repeated after output buffer is drained. Warning: Until flush is complete, client SHOULD NOT swap, reduce or extend input stream. When flush is complete, output data will be sufficient for decoder to re- produce all the given input. BROTLI_OPERATION_FINISH Finalize the stream. Actual finalization is performed when input stream is depleted and there is enough space in output stream. This means that client should repeat BROTLI_OPERATION_FINISH operation until available_in becomes 0, and BrotliEncoderHasMoreOutput returns BROTLI_FALSE. If output is acquired via BrotliEncoderTakeOutput, then operation should be repeated after output buffer is drained. Warning: Until finalization is complete, client SHOULD NOT swap, reduce or ex- tend input stream. Helper function BrotliEncoderIsFinished checks if stream is finalized and output fully dumped. Adding more input data to finalized stream is impossible. BROTLI_OPERATION_EMIT_METADATA Emit metadata block to stream. Metadata is opaque to Brotli: neither encoder, nor decoder processes this data or relies on it. It may be used to pass some extra information from encoder client to decoder client without interfering with main data stream. Note: Encoder may emit empty metadata blocks internally, to pad encoded stream to byte boundary. Warning: Until emitting metadata is complete client SHOULD NOT swap, reduce or extend input stream. The whole content of input buffer is considered to be the content of metadata block. Do NOT append metadata to input stream, before it is depleted with other operations. Stream is soft-flushed before metadata block is emitted. Metadata block MUST be no longer than than 16MiB. enum BrotliEncoderParameter Options to be used with BrotliEncoderSetParameter. Enumerator BROTLI_PARAM_MODE Tune encoder for specific input. BrotliEncoderMode enumerates all available values. BROTLI_PARAM_QUALITY The main compression speed-density lever. The higher the quality, the slower the compression. Range is from BROTLI_MIN_QUALITY to BROTLI_MAX_QUALITY. BROTLI_PARAM_LGWIN Recommended sliding LZ77 window size. Encoder may reduce this value, e.g. if input is much smaller than window size. Window size is (1 << value) - 16. Range is from BROTLI_MIN_WINDOW_BITS to BROTLI_MAX_WINDOW_BITS. BROTLI_PARAM_LGBLOCK Recommended input block size. Encoder may reduce this value, e.g. if input is much smaller than input block size. Range is from BROTLI_MIN_INPUT_BLOCK_BITS to BROTLI_MAX_INPUT_BLOCK_BITS. Note: Bigger input block size allows better compression, but consumes more memory. The rough formula of memory used for temporary input storage is 3 << lgBlock. BROTLI_PARAM_DISABLE_LITERAL_CONTEXT_MODELING Flag that affects usage of 'literal context modeling' format fea- ture. This flag is a 'decoding-speed vs compression ratio' trade- off. BROTLI_PARAM_SIZE_HINT Estimated total input size for all BrotliEncoderCompressStream calls. The default value is 0, which means that the total input size is unknown. BROTLI_PARAM_LARGE_WINDOW Flag that determines if 'Large Window Brotli' is used. BROTLI_PARAM_NPOSTFIX Recommended number of postfix bits (NPOSTFIX). Encoder may change this value. Range is from 0 to BROTLI_MAX_NPOSTFIX. BROTLI_PARAM_NDIRECT Recommended number of direct distance codes (NDIRECT). Encoder may change this value. Range is from 0 to (15 << NPOSTFIX) in steps of (1 << NPOSTFIX). BROTLI_PARAM_STREAM_OFFSET Number of bytes of input stream already processed by a different in- stance. Note: It is important to configure all the encoder instances with same para- meters (except this one) in order to allow all the encoded parts obey the same restrictions implied by header. If offset is not 0, then stream header is omitted. In any case output start is byte aligned, so for proper streams stitching 'predecessor' stream must be flushed. Range is not artificially limited, but all the values greater or equal to maximal window size have the same effect. Values greater than 2**30 are not allowed. Function Documentation BROTLI_BOOL BrotliEncoderAttachPreparedDictionary (BrotliEncoderState * state, const BrotliEncoderPreparedDictionary * dictionary) Attaches a prepared dictionary of any type to the encoder. Can be used mul- tiple times to attach multiple dictionaries. The dictionary type was deter- mined by BrotliEncoderPrepareDictionary. Multiple raw prefix dictionaries and/or max 1 serialized dictionary with custom words can be attached. Returns: BROTLI_FALSE in case of error BROTLI_TRUE otherwise BROTLI_BOOL BrotliEncoderCompress (int quality, int lgwin, BrotliEncoderMode mode, size_t input_size, const uint8_t input_buffer[input_size], size_t * encoded_size, uint8_t encoded_buffer[*encoded_size]) Performs one-shot memory-to-memory compression. Compresses the data in in- put_buffer into encoded_buffer, and sets *encoded_size to the compressed length. Note: If BrotliEncoderMaxCompressedSize(input_size) returns non-zero value, then output is guaranteed to be no longer than that. If lgwin is greater than BROTLI_MAX_WINDOW_BITS then resulting stream might be incompatible with RFC 7932; to decode such streams, decoder should be configured with BROTLI_DECODER_PARAM_LARGE_WINDOW = 1 Parameters: quality quality parameter value, e.g. BROTLI_DEFAULT_QUALITY lgwin lgwin parameter value, e.g. BROTLI_DEFAULT_WINDOW mode mode parameter value, e.g. BROTLI_DEFAULT_MODE input_size size of input_buffer input_buffer input data buffer with at least input_size addressable bytes encoded_size in: size of encoded_buffer; out: length of compressed data written to encoded_buffer, or 0 if com- pression fails encoded_buffer compressed data destination buffer Returns: BROTLI_FALSE in case of compression error BROTLI_FALSE if output buffer is too small BROTLI_TRUE otherwise BROTLI_BOOL BrotliEncoderCompressStream (BrotliEncoderState * state, BrotliEncoderOperation op, size_t * available_in, const uint8_t ** next_in, size_t * available_out, uint8_t ** next_out, size_t * total_out) Compresses input stream to output stream. The values *available_in and *available_out must specify the number of bytes addressable at *next_in and *next_out respectively. When *available_out is 0, next_out is allowed to be NULL. After each call, *available_in will be decremented by the amount of input bytes consumed, and the *next_in pointer will be incremented by that amount. Similarly, *available_out will be decremented by the amount of out- put bytes written, and the *next_out pointer will be incremented by that amount. total_out, if it is not a null-pointer, will be set to the number of bytes compressed since the last state initialization. Internally workflow consists of 3 tasks: 1. (optionally) copy input data to internal buffer 2. actually compress data and (optionally) store it to internal buffer 3. (optionally) copy compressed bytes from internal buffer to output stream Whenever all 3 tasks can't move forward anymore, or error occurs, this method returns the control flow to caller. op is used to perform flush, finish the stream, or inject metadata block. See BrotliEncoderOperation for more information. Flushing the stream means forcing encoding of all input passed to encoder and completing the current output block, so it could be fully decoded by stream decoder. To perform flush set op to BROTLI_OPERATION_FLUSH. Under some circumstances (e.g. lack of output stream capacity) this operation would require several calls to BrotliEncoderCompressStream. The method must be called again until both input stream is depleted and encoder has no more output (see BrotliEncoderHasMoreOutput) after the method is called. Finishing the stream means encoding of all input passed to encoder and adding specific 'final' marks, so stream decoder could determine that stream is complete. To perform finish set op to BROTLI_OPERATION_FINISH. Under some circumstances (e.g. lack of output stream capacity) this opera- tion would require several calls to BrotliEncoderCompressStream. The method must be called again until both input stream is depleted and encoder has no more output (see BrotliEncoderHasMoreOutput) after the method is called. Warning: When flushing and finishing, op should not change until operation is complete; input stream should not be swapped, reduced or extended as well. Parameters: state encoder instance op requested operation available_in in: amount of available input; out: amount of unused input next_in pointer to the next input byte available_out in: length of output buffer; out: remaining size of output buffer next_out compressed output buffer cursor; can be NULL if available_out is 0 total_out number of bytes produced so far; can be NULL Returns: BROTLI_FALSE if there was an error BROTLI_TRUE otherwise BrotliEncoderState* BrotliEncoderCreateInstance (brotli_alloc_func al- loc_func, brotli_free_func free_func, void * opaque) Creates an instance of BrotliEncoderState and initializes it. alloc_func and free_func MUST be both zero or both non-zero. In the case they are both zero, default memory allocators are used. opaque is passed to alloc_func and free_func when they are called. free_func has to return without doing anything when asked to free a NULL pointer. Parameters: alloc_func custom memory allocation function free_func custom memory free function opaque custom memory manager handle Returns: 0 if instance can not be allocated or initialized pointer to initialized BrotliEncoderState otherwise void BrotliEncoderDestroyInstance (BrotliEncoderState * state) Deinitializes and frees BrotliEncoderState instance. Parameters: state decoder instance to be cleaned up and deallocated BROTLI_BOOL BrotliEncoderHasMoreOutput (BrotliEncoderState * state) Checks if encoder has more output. Parameters: state encoder instance Returns: BROTLI_TRUE, if encoder has some unconsumed output BROTLI_FALSE otherwise BROTLI_BOOL BrotliEncoderIsFinished (BrotliEncoderState * state) Checks if encoder instance reached the final state. Parameters: state encoder instance Returns: BROTLI_TRUE if encoder is in a state where it reached the end of the input and produced all of the output BROTLI_FALSE otherwise size_t BrotliEncoderMaxCompressedSize (size_t input_size) Calculates the output size bound for the given input_size. Warning: Result is only valid if quality is at least 2 and, in case BrotliEn- coderCompressStream was used, no flushes (BROTLI_OPERATION_FLUSH) were performed. Parameters: input_size size of projected input Returns: 0 if result does not fit size_t BrotliEncoderPreparedDictionary* BrotliEncoderPrepareDictionary (BrotliSharedDictionaryType type, size_t data_size, const uint8_t data[data_size], int quality, brotli_alloc_func alloc_func, brotli_free_func free_func, void * opaque) Prepares a shared dictionary from the given file format for the encoder. alloc_func and free_func MUST be both zero or both non-zero. In the case they are both zero, default memory allocators are used. opaque is passed to alloc_func and free_func when they are called. free_func has to return without doing anything when asked to free a NULL pointer. Warning: Created instance is 'lean'; it does not contain copy of data, rather it contains only pointer to it; therefore, data MUST outlive the created instance. Parameters: type type of dictionary stored in data data_size size of data buffer data pointer to the dictionary data quality the maximum Brotli quality to prepare the dictionary for, use BROTLI_MAX_QUALITY by default alloc_func custom memory allocation function free_func custom memory free function opaque custom memory manager handle BROTLI_BOOL BrotliEncoderSetParameter (BrotliEncoderState * state, BrotliEn- coderParameter param, uint32_t value) Sets the specified parameter to the given encoder instance. Parameters: state encoder instance param parameter to set value new parameter value Returns: BROTLI_FALSE if parameter is unrecognized, or value is invalid BROTLI_FALSE if value of parameter can not be changed at current en- coder state (e.g. when encoding is started, window size might be al- ready encoded and therefore it is impossible to change it) BROTLI_TRUE if value is accepted Warning: invalid values might be accepted in case they would not break encoding process. const uint8_t* BrotliEncoderTakeOutput (BrotliEncoderState * state, size_t * size) Acquires pointer to internal output buffer. This method is used to make language bindings easier and more efficient: 1. push data to BrotliEncoderCompressStream, until BrotliEncoderHasMore- Output returns BROTLI_TRUE 2. use BrotliEncoderTakeOutput to peek bytes and copy to language-specific entity Also this could be useful if there is an output stream that is able to con- sume all the provided data (e.g. when data is saved to file system). Attention: After every call to BrotliEncoderTakeOutput *size bytes of output are considered consumed for all consecutive calls to the instance methods; returned pointer becomes invalidated as well. Note: Encoder output is not guaranteed to be contiguous. This means that af- ter the size-unrestricted call to BrotliEncoderTakeOutput, immediate next call to BrotliEncoderTakeOutput may return more data. Parameters: state encoder instance size in: number of bytes caller is ready to take, 0 if any amount could be handled; out: amount of data pointed by returned pointer and considered con- sumed; out value is never greater than in value, unless it is 0 Returns: pointer to output data uint32_t BrotliEncoderVersion (void) Gets an encoder library version. Look at BROTLI_MAKE_HEX_VERSION for more information. Author Generated automatically by Doxygen for Brotli from the source code. Brotli August 2021 encode.h(3)
NAME | SYNOPSIS | Detailed Description | Macro Definition Documentation | Typedef Documentation | Enumeration Type Documentation | Function Documentation | Author
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