expand_block

SFL
Version 2.11

`expand_block`

#include "sflcomp.h"
word
expand_block (
    const byte *src,
    byte *dst,
    word src_size)

Synopsis

Expands a block of data previously compressed using the compress block() function. The compressed block is passed in src; the expanded result in dst. dst must be large enough to accomodate the largest possible decompressed block. Returns the size of the uncompressed data.

Source Code - (sflcomp.c)

{
    word SymbolAddress;
    word ChunkSize;
    word Counter;
    word Command = 0;
    word src_index = 1;
    word dst_size = 0;
    byte Bit = 0;

    if (src [0] == FLAG_COPY)
      {
        for (dst_size = 1; dst_size < src_size; dst_size++)
            dst [dst_size - 1] = src [dst_size];
        return (src_size - 1);
      }
    while (src_index < src_size)
      {
        if (Bit == 0)
          {
            Command  = src [src_index++] << 8;
            Command += src [src_index++];
            Bit = 16;
          }
        if (Command & 0x8000)
          {
            SymbolAddress =  (word) (src [src_index++] << 4);
            SymbolAddress += (word) (src [src_index] >> 4);
            if (SymbolAddress)
              {
                ChunkSize = (word) (src [src_index++] & 0x0f) + 3;
                SymbolAddress = dst_size - SymbolAddress;
                for (Counter = 0; Counter < ChunkSize; Counter++)
                    dst [dst_size++] = dst [SymbolAddress++];
              }
            else
              {
                ChunkSize  = (word) (src [src_index++] << 8);
                ChunkSize += (word) (src [src_index++] + 16);
                for (Counter = 0; Counter < ChunkSize; Counter++)
                    dst [dst_size++] = src [src_index];
                src_index++;
              }
          }
        else
            dst [dst_size++] = src [src_index++];

        Command <<= 1;
        Bit--;
      }
    return (dst_size);
}

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