decode.h(3)

NAME
decode.h - API for Brotli decompression.

SYNOPSIS

  Macros
#define BROTLI_DECODER_ERROR_CODES_LIST(BROTLI_ERROR_CODE, SEPARATOR)
Template that evaluates items of BrotliDecoderErrorCode.
#define BROTLI_LAST_ERROR_CODE BROTLI_DECODER_ERROR_UNREACHABLE
The value of the last error code, negative integer.

  Typedefs
typedef void(* brotli_decoder_metadata_chunk_func) (void *opaque, const uint8_t *data, size_t size)
Callback to fire on metadata block chunk becomes available.
typedef void(* brotli_decoder_metadata_start_func) (void *opaque, size_t size)
Callback to fire on metadata block start.
typedef enum BrotliDecoderParameter BrotliDecoderParameter
Options to be used with BrotliDecoderSetParameter.
typedef struct BrotliDecoderStateStruct BrotliDecoderState
Opaque structure that holds decoder state.

  Enumerations

  Functions
BROTLI_BOOL BrotliDecoderAttachDictionary (BrotliDecoderState *state, BrotliSharedDictionaryType type, size_t data_size, const uint8_t data[data_size])
Adds LZ77 prefix dictionary, adds or replaces built-in static dictionary and transforms.
BrotliDecoderState * BrotliDecoderCreateInstance (brotli_alloc_func alloc_func, brotli_free_func free_func, void *opaque)
Creates an instance of BrotliDecoderState and initializes it.
BrotliDecoderResult BrotliDecoderDecompress (size_t encoded_size, const uint8_t encoded_buffer[encoded_size], size_t *decoded_size, uint8_t decoded_buffer[*decoded_size])
Performs one-shot memory-to-memory decompression.
BrotliDecoderResult BrotliDecoderDecompressStream (BrotliDecoderState *state, size_t *available_in, const uint8_t **next_in, size_t *available_out, uint8_t **next_out, size_t *total_out)
Decompresses the input stream to the output stream.
void BrotliDecoderDestroyInstance (BrotliDecoderState *state)
Deinitializes and frees BrotliDecoderState instance.
const char * BrotliDecoderErrorString (BrotliDecoderErrorCode c)
Converts error code to a c-string.
BrotliDecoderErrorCode BrotliDecoderGetErrorCode (const BrotliDecoderState *state)
Acquires a detailed error code.
BROTLI_BOOL BrotliDecoderHasMoreOutput (const BrotliDecoderState *state)
Checks if decoder has more output.
BROTLI_BOOL BrotliDecoderIsFinished (const BrotliDecoderState *state)
Checks if decoder instance reached the final state.
BROTLI_BOOL BrotliDecoderIsUsed (const BrotliDecoderState *state)
Checks if instance has already consumed input.
void BrotliDecoderSetMetadataCallbacks (BrotliDecoderState *state, brotli_decoder_metadata_start_func start_func, brotli_decoder_metadata_chunk_func chunk_func, void *opaque)
Sets callback for receiving metadata blocks.
BROTLI_BOOL BrotliDecoderSetParameter (BrotliDecoderState *state, BrotliDecoderParameter param, uint32_t value)
Sets the specified parameter to the given decoder instance.
const uint8_t * BrotliDecoderTakeOutput (BrotliDecoderState *state, size_t *size)
Acquires pointer to internal output buffer.
uint32_t BrotliDecoderVersion (void)
Gets a decoder library version.

Detailed Description

API for Brotli decompression.

Macro Definition Documentation

  #define BROTLI_DECODER_ERROR_CODES_LIST(BROTLI_ERROR_CODE, SEPARATOR)

Template that evaluates items of BrotliDecoderErrorCode. Example:

// Log Brotli error code.
switch (brotliDecoderErrorCode) {
#define CASE_(PREFIX, NAME, CODE)   case BROTLI_DECODER ## PREFIX ## NAME:     LOG(INFO) << "error code:" << #NAME;     break;
#define NEWLINE_
BROTLI_DECODER_ERROR_CODES_LIST(CASE_, NEWLINE_)
#undef CASE_
#undef NEWLINE_
  default: LOG(FATAL) << "unknown brotli error code";
}

  #define BROTLI_LAST_ERROR_CODE BROTLI_DECODER_ERROR_UNREACHABLE

The value of the last error code, negative integer. All other error code values are in the range from BROTLI_LAST_ERROR_CODE to -1. There are also 4 other possible non-error codes 0 .. 3 in BrotliDecoderErrorCode enumeration.

Typedef Documentation

  typedef void(* brotli_decoder_metadata_chunk_func) (void *opaque, const uint8_t *data, size_t size)

Callback to fire on metadata block chunk becomes available. This function can be invoked multiple times per metadata block; block should be considered finished when sum of size matches the announced metadata block size. Chunks contents pointed by data are transient and shouln not be accessed after leaving the callback.

Parameters:
    opaque callback handle
    data pointer to metadata contents
    size size of metadata block chunk, at least 1

  typedef void(* brotli_decoder_metadata_start_func) (void *opaque, size_t size)

Callback to fire on metadata block start. After this callback is fired, if size is not 0, it is followed by brotli_decoder_metadata_chunk_func as more metadata block contents become accessible.

Parameters:
    opaque callback handle
    size size of metadata block

  typedef enum BrotliDecoderParameter BrotliDecoderParameter

Options to be used with BrotliDecoderSetParameter.

  typedef struct BrotliDecoderStateStruct BrotliDecoderState

Opaque structure that holds decoder state. Allocated and initialized with BrotliDecoderCreateInstance. Cleaned up and deallocated with BrotliDecoderDestroyInstance.

Enumeration Type Documentation

  enum BrotliDecoderErrorCode

Error code for detailed logging / production debugging. See BrotliDecoderGetErrorCode and BROTLI_LAST_ERROR_CODE.

  enum BrotliDecoderParameter

Options to be used with BrotliDecoderSetParameter.

Enumerator

BROTLI_DECODER_PARAM_DISABLE_RING_BUFFER_REALLOCATION
    Disable 'canny' ring buffer allocation strategy. Ring buffer is allocated according to window size, despite the real size of the content.

BROTLI_DECODER_PARAM_LARGE_WINDOW
    Flag that determines if 'Large Window Brotli' is used.

  enum BrotliDecoderResult

Result type for BrotliDecoderDecompress and BrotliDecoderDecompressStream functions.

Enumerator

BROTLI_DECODER_RESULT_ERROR
    Decoding error, e.g. corrupted input or memory allocation problem.

BROTLI_DECODER_RESULT_SUCCESS
    Decoding successfully completed.

BROTLI_DECODER_RESULT_NEEDS_MORE_INPUT
    Partially done; should be called again with more input.

BROTLI_DECODER_RESULT_NEEDS_MORE_OUTPUT
    Partially done; should be called again with more output.

Function Documentation

  BROTLI_BOOL BrotliDecoderAttachDictionary (BrotliDecoderState * state, BrotliSharedDictionaryType type, size_t data_size, const uint8_t data[data_size])

Adds LZ77 prefix dictionary, adds or replaces built-in static dictionary and transforms. Attached dictionary ownership is not transferred. Data provided to this method should be kept accessible until decoding is finished and decoder instance is destroyed.

Note:
    Dictionaries can NOT be attached after actual decoding is started.

Parameters:
    state decoder instance
    type dictionary data format
    data_size length of memory region pointed by data
    data dictionary data in format corresponding to type

Returns:
    BROTLI_FALSE if dictionary is corrupted, or dictionary count limit is reached

    BROTLI_TRUE if dictionary is accepted / attached

  BrotliDecoderState* BrotliDecoderCreateInstance (brotli_alloc_func alloc_func, brotli_free_func free_func, void * opaque)

Creates an instance of BrotliDecoderState and initializes it. The instance can be used once for decoding and should then be destroyed with BrotliDecoderDestroyInstance, it cannot be reused for a new decoding session.

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 BrotliDecoderState otherwise

  BrotliDecoderResult BrotliDecoderDecompress (size_t encoded_size, const uint8_t encoded_buffer[encoded_size], size_t * decoded_size, uint8_t decoded_buffer[*decoded_size])

Performs one-shot memory-to-memory decompression. Decompresses the data in encoded_buffer into decoded_buffer, and sets *decoded_size to the decompressed length.

Parameters:
    encoded_size size of encoded_buffer
    encoded_buffer compressed data buffer with at least encoded_size addressable bytes
    decoded_size in: size of decoded_buffer;
     out: length of decompressed data written to decoded_buffer
    decoded_buffer decompressed data destination buffer

Returns:
    BROTLI_DECODER_RESULT_ERROR if input is corrupted, memory allocation failed, or decoded_buffer is not large enough;

    BROTLI_DECODER_RESULT_SUCCESS otherwise

  BrotliDecoderResult BrotliDecoderDecompressStream (BrotliDecoderState * state, size_t * available_in, const uint8_t ** next_in, size_t * available_out, uint8_t ** next_out, size_t * total_out)

Decompresses the input stream to the 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 output 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 decompressed since the last state initialization.

Note:
    Input is never overconsumed, so next_in and available_in could be passed to the next consumer after decoding is complete.

Parameters:
    state decoder instance
    available_in in: amount of available input;
     out: amount of unused input
    next_in pointer to the next compressed byte
    available_out in: length of output buffer;
     out: remaining size of output buffer
    next_out output buffer cursor; can be NULL if available_out is 0
    total_out number of bytes decompressed so far; can be NULL

Returns:
    BROTLI_DECODER_RESULT_ERROR if input is corrupted, memory allocation failed, arguments were invalid, etc.; use BrotliDecoderGetErrorCode to get detailed error code

    BROTLI_DECODER_RESULT_NEEDS_MORE_INPUT decoding is blocked until more input data is provided

    BROTLI_DECODER_RESULT_NEEDS_MORE_OUTPUT decoding is blocked until more output space is provided

    BROTLI_DECODER_RESULT_SUCCESS decoding is finished, no more input might be consumed and no more output will be produced

  void BrotliDecoderDestroyInstance (BrotliDecoderState * state)

Deinitializes and frees BrotliDecoderState instance.

Parameters:
    state decoder instance to be cleaned up and deallocated

  BrotliDecoderErrorCode BrotliDecoderGetErrorCode (const BrotliDecoderState * state)

Acquires a detailed error code. Should be used only after BrotliDecoderDecompressStream returns BROTLI_DECODER_RESULT_ERROR.

See also BrotliDecoderErrorString

Parameters:
    state decoder instance

Returns:
    last saved error code

  BROTLI_BOOL BrotliDecoderHasMoreOutput (const BrotliDecoderState * state)

Checks if decoder has more output.

Parameters:
    state decoder instance

Returns:
    BROTLI_TRUE, if decoder has some unconsumed output

    BROTLI_FALSE otherwise

  BROTLI_BOOL BrotliDecoderIsFinished (const BrotliDecoderState * state)

Checks if decoder instance reached the final state.

Parameters:
    state decoder instance

Returns:
    BROTLI_TRUE if decoder is in a state where it reached the end of the input and produced all of the output

    BROTLI_FALSE otherwise

  BROTLI_BOOL BrotliDecoderIsUsed (const BrotliDecoderState * state)

Checks if instance has already consumed input. Instance that returns BROTLI_FALSE is considered 'fresh' and could be reused.

Parameters:
    state decoder instance

Returns:
    BROTLI_TRUE if decoder has already used some input bytes

    BROTLI_FALSE otherwise

  void BrotliDecoderSetMetadataCallbacks (BrotliDecoderState * state, brotli_decoder_metadata_start_func start_func, brotli_decoder_metadata_chunk_func chunk_func, void * opaque)

Sets callback for receiving metadata blocks.

Parameters:
    state decoder instance
    start_func callback on metadata block start
    chunk_func callback on metadata block chunk
    opaque callback handle

  BROTLI_BOOL BrotliDecoderSetParameter (BrotliDecoderState * state, BrotliDecoderParameter param, uint32_t value)

Sets the specified parameter to the given decoder instance.

Parameters:
    state decoder instance
    param parameter to set
    value new parameter value

Returns:
    BROTLI_FALSE if parameter is unrecognized, or value is invalid

    BROTLI_TRUE if value is accepted

  const uint8_t* BrotliDecoderTakeOutput (BrotliDecoderState * 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 BrotliDecoderDecompressStream, until BROTLI_DECODER_RESULT_NEEDS_MORE_OUTPUT is reported

2.  use BrotliDecoderTakeOutput to peek bytes and copy to language-specific entity

Also this could be useful if there is an output stream that is able to consume all the provided data (e.g. when data is saved to file system).

Attention:
    After every call to BrotliDecoderTakeOutput *size bytes of output are considered consumed for all consecutive calls to the instance methods; returned pointer becomes invalidated as well.

Note:
    Decoder output is not guaranteed to be contiguous. This means that after the size-unrestricted call to BrotliDecoderTakeOutput, immediate next call to BrotliDecoderTakeOutput may return more data.

Parameters:
    state decoder 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 consumed;
     out value is never greater than in value, unless it is 0

Returns:
    pointer to output data

  uint32_t BrotliDecoderVersion (void)

Gets a decoder library version. Look at BROTLI_MAKE_HEX_VERSION for more information.

Author

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