%% options copyright owner = Dirk Krause copyright year = 2015-xxxx license = bsd %% header /** @file dk4rld.h Run-length decoder. Use dk4rld_init() to initialize the decoder before feeding data to it. Feed the encoded data into the decoder byte by byte, use the dk4rld_add() function. If the function returns DK4_EDSTM_ACCEPT, the input was successfully stored into the internal data structures, not need for further action. If the function returns DK4_EDSTM_FINISHED, an output secquence was completed, either a run or a literal byte sequence. Use dk4rld_output() to retrieve output data. If the dk4rld_add function returns DK4_EDSTM_STOP, an end of data (EOD) marker was found; do not feed further bytes into the decoder. After feeding all input bytes into the decoder, use dk4rld_finish() to check syntax. If the function returns DK4_EDSTM_ERROR, the input data stream was not properly run-length encoded. */ #include "dk4error.h" /** Run length decoder. */ typedef struct { unsigned char ob[128]; /**< Output buffer. */ size_t oused; /**< Number of used bytes in ob. */ size_t ll; /**< Number of expected bytes. */ int st; /**< Current state. */ } dk4_rl_dec_t; #ifdef __cplusplus extern "C" { #endif /** Initialize decoder. @param dec Decoder to initialize. @param erp Error report, may be NULL. Error codes: - DK4_E_INVALID_ARGUMENTS if enc is NULL. */ void dk4rld_init(dk4_rl_dec_t *dec, dk4_er_t *erp); /** Add one encoded byte to decoder. @param dec Decoder. @param inbyte Byte to process. @param erp Error report, may be NULL. @return Action to take, one from: - DK4_EDSTM_ACCEPT
if the byte was successfully added to the internal data structures, no further action necessary. - DK4_EDSTM_FINISHED
if output is available, use dk4rld_output() to retrieve output. - DK4_EDSTM_STOP
if an EOD marker was detected. Do not feed further bytes to the decoder. - DK4_EDSTM_ERROR
if an error occured. Error codes: - DK4_E_INVALID_ARGUMENTS if enc is NULL. */ int dk4rld_add(dk4_rl_dec_t *dec, unsigned char inbyte, dk4_er_t *erp); /** Finish decoding. @param dec Decoder. @param erp Error report, may be NULL. @return Action to take, one from: - DK4_EDSTM_ACCEPT
if no remaining data is stored in the decoder, no further action necessary. - DK4_EDSTM_FINISHED
if output is available, use dk4rld_output() to retrieve output. - DK4_EDSTM_ERROR
if an error occured. Error codes: - DK4_E_INVALID_ARGUMENTS
if enc is NULL. - DK4_E_SYNTAX
if data indicated by the run-length byte or literally-length byte is missing. */ int dk4rld_finish(dk4_rl_dec_t *dec, dk4_er_t *erp); /** Retrieve decoder output. @param dptr Address of pointer to set to decoder output, should be initialized to NULL. @param szptr Address of variable to receive buffer size, should be initialized to 0. @param dec Decoder. @param erp Error report, may be NULL. @return 1 if data is available, 0 otherwise. Error codes: - DK4_E_INVALID_ARGUMENTS if enc is NULL. */ int dk4rld_output( const unsigned char **dptr, size_t *szptr, dk4_rl_dec_t *dec, dk4_er_t *erp ); #ifdef __cplusplus } #endif %% module #include "dk4rld.h" #include "dk4edstm.h" #include "dk4mem.h" $!trace-include /** Decoder states. */ enum { /** Start state, exepect run length or literal data length. */ RLD_ST_EXPECT_KEY_BYTE = 0, /** Expect byte value for run. */ RLD_ST_EXPECT_RUN_BYTE , /** Expect literal byte. */ RLD_ST_EXPECT_LITERAL_BYTE , /** No further input accepted as EOD marker was found. */ RLD_ST_EOD_FOUND }; void dk4rld_init(dk4_rl_dec_t *dec, dk4_er_t *erp) { $? "+ dk4rld_init" if (NULL != dec) { DK4_MEMRES(dec, sizeof(dk4_rl_dec_t)); dec->oused = 0; dec->ll = 0; dec->st = RLD_ST_EXPECT_KEY_BYTE; } else { dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS); } $? "- dk4rld_init" } int dk4rld_add(dk4_rl_dec_t *dec, unsigned char inbyte, dk4_er_t *erp) { int back = DK4_EDSTM_ERROR; $? "+ dk4rld_add" if (NULL != dec) { switch (dec->st) { case RLD_ST_EXPECT_KEY_BYTE : { if ((unsigned char)128 > inbyte) { /* Literal byte sequence */ dec->st = RLD_ST_EXPECT_LITERAL_BYTE; dec->ll = (size_t)inbyte + 1; back = DK4_EDSTM_ACCEPT; } else { if ((unsigned char)128 < inbyte) { /* Run of equal bytes */ dec->st = RLD_ST_EXPECT_RUN_BYTE; dec->ll = (size_t)257 - (size_t)inbyte; back = DK4_EDSTM_ACCEPT; } else { /* EOD marker found */ dec->st = RLD_ST_EOD_FOUND; back = DK4_EDSTM_STOP; } } } break; case RLD_ST_EXPECT_RUN_BYTE : { dk4mem_set(&(dec->ob[0]), dec->ll, inbyte, NULL); dec->oused = dec->ll; dec->st = RLD_ST_EXPECT_KEY_BYTE; back = DK4_EDSTM_FINISHED; } break; case RLD_ST_EXPECT_LITERAL_BYTE : { dec->ob[0] = inbyte; dec->oused = 1; dec->ll -= 1; if (0 == dec->ll) { dec->st = RLD_ST_EXPECT_KEY_BYTE; } back = DK4_EDSTM_FINISHED; } break; default : { dk4error_set_simple_error_code(erp, DK4_E_SYNTAX); } break; } } else { dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS); } $? "- dk4rld_add %d", back return back; } int dk4rld_finish(dk4_rl_dec_t *dec, dk4_er_t *erp) { int back = DK4_EDSTM_ERROR; $? "+ dk4rld_finish" if (NULL != dec) { switch (dec->st) { case RLD_ST_EXPECT_KEY_BYTE : case RLD_ST_EOD_FOUND : { back = DK4_EDSTM_ACCEPT; } break; default : { dk4error_set_simple_error_code(erp, DK4_E_SYNTAX); } break; } } else { dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS); } $? "- dk4rld_finish %d", back return back; } int dk4rld_output( const unsigned char **dptr, size_t *szptr, dk4_rl_dec_t *dec, dk4_er_t *erp ) { int back = 0; $? "+ dk4rld_output" if (NULL != dec) { if (0 < dec->oused) { *dptr = &(dec->ob[0]); *szptr = dec->oused; back = 1; } else { *dptr = NULL; *szptr = 0; } } else { dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS); } $? "- dk4rld_output %d", back return back; }