Method: LZ4::BlockDecoder#update

Defined in:

ext/blockapi.c

#update(src, dest = "") ⇒ Object #update(src, max_dest_size, dest = "") ⇒ Object Also known as: decode, decompress, uncompress

Decode block lz4 data of stream block.

Given arguments and return values are same as LZ4#block_decode. See LZ4#block_decode for about its.

出力先は、max_dest_size が与えられていない場合、必要に応じて自動的に拡張されます。この場合、いったん圧縮された LZ4 データを走査するため、事前に僅かな CPU 時間を必要とします。

# File 'ext/blockapi.c', line 862

static VALUE
blkdec_update(int argc, VALUE argv[], VALUE dec)
{
    struct blockdecoder *p = getdecoder(dec);
    if (!p->context) { rb_raise(extlz4_eError, "need reset (context not initialized)"); }
    VALUE src, dest;
    size_t maxsize;
    blockprocess_args(argc, argv, &src, &dest, &maxsize, NULL, aux_lz4_scansize);
    const char *srcp;
    size_t srcsize;
    RSTRING_GETMEM(src, srcp, srcsize);
    LZ4_setStreamDecode(p->context, p->dictbuf, aux_size2int(p->dictsize));
    int s = aux_LZ4_decompress_safe_continue(p->context, srcp, RSTRING_PTR(dest), aux_size2int(srcsize), aux_size2int(maxsize));
    if (s < 0) {
        rb_raise(extlz4_eError,
                "`max_dest_size' too small, or corrupt lz4'd data");
    }
    rb_str_set_len(dest, s);

    /* copy prefix */
    if ((size_t)s < sizeof(p->dictbuf)) {
        ssize_t discard = (p->dictsize + s) - sizeof(p->dictbuf);
        if (discard > 0) {
            size_t remain = p->dictsize - discard;
            memmove(p->dictbuf, (const char *)(p->dictbuf + discard), remain);
            p->dictsize = remain;
        }

        memcpy(p->dictbuf + p->dictsize, RSTRING_PTR(dest), s);
        p->dictsize += s;
    } else {
        memcpy(p->dictbuf, RSTRING_END(dest) - sizeof(p->dictbuf), sizeof(p->dictbuf));
        p->dictsize = sizeof(p->dictbuf);
    }

    return dest;
}