Zlib-ng deflate symbol macros

deflate_sym_macros.h

/* ===========================================================================
 * Symbol buffer write/read macros.
 *
 * The symbol buffer stores literal and distance/length pairs. The storage
 * format differs based on LIT_MEM (separate buffers) vs sym_buf (interleaved),
 * and on whether the platform supports fast unaligned 32-bit access
 * (OPTIMAL_CMP >= 32), which allows packing a 3-byte symbol into a single
 * 32-bit write/read.
 *
 * SYM_WRITE_LIT and SYM_WRITE_DIST write a symbol and advance sym_next.
 * SYM_READ reads a symbol and advances sx.
 */
#ifdef LIT_MEM

#define SYM_WRITE_LIT(s, sym_next, c) { \
    (s)->d_buf[(sym_next)] = 0; \
    (s)->l_buf[(sym_next)] = (c); \
    (sym_next) += 1; \
}
#define SYM_WRITE_DIST(s, sym_next, dist, len) { \
    (s)->d_buf[(sym_next)] = (uint16_t)(dist); \
    (s)->l_buf[(sym_next)] = (uint8_t)(len); \
    (sym_next) += 1; \
}
#define SYM_READ(s, sx, dist, lc) { \
    (dist) = (s)->d_buf[(sx)]; \
    (lc) = (s)->l_buf[(sx)]; \
    (sx) += 1; \
}

#else /* !LIT_MEM */

#if OPTIMAL_CMP >= 32

#define SYM_WRITE_LIT(s, sym_next, c) { \
    zng_memwrite_4(&(s)->sym_buf[(sym_next)], Z_U32_TO_LE((uint32_t)(c) << 16)); \
    (sym_next) += 3; \
}
#define SYM_WRITE_DIST(s, sym_next, dist, len) { \
    zng_memwrite_4(&(s)->sym_buf[(sym_next)], Z_U32_TO_LE((dist) | ((uint32_t)(len) << 16))); \
    (sym_next) += 3; \
}
#define SYM_READ(s, sx, dist, lc) { \
    uint32_t _val = Z_U32_FROM_LE(zng_memread_4(&(s)->sym_buf[(sx)])); \
    (dist) = _val & 0xffff; \
    (lc) = (_val >> 16) & 0xff; \
    (sx) += 3; \
}

#else /* OPTIMAL_CMP < 32 */

#define SYM_WRITE_LIT(s, sym_next, c) { \
    (s)->sym_buf[(sym_next)]   = 0; \
    (s)->sym_buf[(sym_next)+1] = 0; \
    (s)->sym_buf[(sym_next)+2] = (c); \
    (sym_next) += 3; \
}
#define SYM_WRITE_DIST(s, sym_next, dist, len) { \
    (s)->sym_buf[(sym_next)]   = (uint8_t)(dist); \
    (s)->sym_buf[(sym_next)+1] = (uint8_t)((dist) >> 8); \
    (s)->sym_buf[(sym_next)+2] = (uint8_t)(len); \
    (sym_next) += 3; \
}
#define SYM_READ(s, sx, dist, lc) { \
    (dist) = (s)->sym_buf[(sx)] + ((unsigned)(s)->sym_buf[(sx) + 1] << 8); \
    (lc) = (s)->sym_buf[(sx) + 2]; \
    (sx) += 3; \
}

#endif /* OPTIMAL_CMP >= 32 */
#endif /* LIT_MEM */