decode.h

Section: C Library Functions (3)
Updated: Thu Feb 22 2018
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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 enum BrotliDecoderParameter BrotliDecoderParameter
Options to be used with BrotliDecoderSetParameter.
typedef struct BrotliDecoderStateStruct BrotliDecoderState
Opaque structure that holds decoder state.

Enumerations

Functions

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.
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 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

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.

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

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_VERSION for more information.

Author

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