%% options copyright owner = Dirk Krause copyright year = 2015-xxxx license = bsd %% header /** @file dk4bitsh.h Bit shifting. */ #include "dk4error.h" /** Bit shifter. */ typedef struct { int pos; /**< Current bit position. */ unsigned char obyte; /**< Output byte. */ } dk4_bit_shift_t; #ifdef __cplusplus extern "C" { #endif /** Initialize a bit shifter before using it. @param bs Bit shifter to initialize. @param erp Error report, may be NULL. Error codes: - DK4_E_INVALID_ARGUMENTS if bs is NULL. */ void dk4bit_shift_init(dk4_bit_shift_t *bs, dk4_er_t *erp); /** Add one byte. @param bs Bit shifter. @param bit Bit value, 0 or non-0. @param erp Error report, may be NULL. @return Action to take, one from: - DK4_EDSTM_ACCEPT
if the bit was stored in the bit shifter. No action necessary. - DK4_EDSTM_FINISHED
if one byte was completed by adding the bit. Use dk4bit_shift_output() to retrieve the finished byte. - DK4_EDSTM_ERROR
if an error occured. Error codes: - DK4_E_INVALID_ARGUMENTS
if bs is NULL. */ int dk4bit_shift_add(dk4_bit_shift_t *bs, int bit, dk4_er_t *erp); /** Check for unused content in the bit shifter after adding all bits. @param bs Bit shifter. @param erp Error report, may be NULL. @return Action to take, one from: - DK4_EDSTM_ACCEPT
if no action is required. - DK4_EDSTM_FINISHED
if significant bits are available for a byte. Use dk4bit_shift_output() to retrieve the byte value. - DK4_EDSTM_ERROR
if an error occured. Error codes: - DK4_E_INVALID_ARGUMENTS
if bs is NULL. */ int dk4bit_shift_finish(dk4_bit_shift_t *bs, dk4_er_t *erp); /** Retrieve previous completed byte or final incomplete byte. @param bs Bit shifter. @param erp Error report, may be NULL. @return Byte value consisting of the last bits added. */ unsigned char dk4bit_shift_output(dk4_bit_shift_t *bs, dk4_er_t *erp); #ifdef __cplusplus } #endif %% module #include "dk4bitsh.h" #include "dk4edstm.h" #include "dk4mem.h" $!trace-include void dk4bit_shift_init(dk4_bit_shift_t *bs, dk4_er_t *erp) { if (NULL != bs) { DK4_MEMRES(bs, sizeof(dk4_bit_shift_t)); bs->pos = 0; bs->obyte = 0x00; } else { dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS); } } int dk4bit_shift_add(dk4_bit_shift_t *bs, int bit, dk4_er_t *erp) { int back = DK4_EDSTM_ERROR; if (NULL != bs) { back = DK4_EDSTM_ACCEPT; switch (bs->pos) { case 0: { if (0 != bit) { bs->obyte = 0x80; } else { bs->obyte = 0x00; } bs->pos = 1; } break; case 1: { if (0 != bit) { bs->obyte |= 0x40; } bs->pos = 2; } break; case 2: { if (0 != bit) { bs->obyte |= 0x20; } bs->pos = 3; } break; case 3: { if (0 != bit) { bs->obyte |= 0x10; } bs->pos = 4; } break; case 4: { if (0 != bit) { bs->obyte |= 0x08; } bs->pos = 5; } break; case 5: { if (0 != bit) { bs->obyte |= 0x04; } bs->pos = 6; } break; case 6: { if (0 != bit) { bs->obyte |= 0x02; } bs->pos = 7; } break; case 7: { if (0 != bit) { bs->obyte |= 0x01; } bs->pos = 0; back = DK4_EDSTM_FINISHED; } break; } } else { dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS); } return back; } int dk4bit_shift_finish(dk4_bit_shift_t *bs, dk4_er_t *erp) { int back = DK4_EDSTM_ERROR; if (NULL != bs) { if (0 != bs->pos) { back = DK4_EDSTM_FINISHED; } else { back = DK4_EDSTM_ACCEPT; } } else { dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS); } return back; } unsigned char dk4bit_shift_output(dk4_bit_shift_t *bs, dk4_er_t *erp) { unsigned char back; if (NULL != bs) { back = bs->obyte; } else { back = 0x00; dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS); } return back; }