forked from Mirror/GodMode9
83 lines
3.1 KiB
C
83 lines
3.1 KiB
C
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#include "codelzss.h"
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#define CODE_COMP_SIZE(f) ((f)->off_size_comp & 0xFFFFFF)
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#define CODE_COMP_END(f) ((int) CODE_COMP_SIZE(f) - (int) (((f)->off_size_comp >> 24) % 0xFF))
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#define CODE_DEC_SIZE(f) (CODE_COMP_SIZE(f) + (f)->addsize_dec)
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#define CODE_SEG_OFFSET(s) (((s) & 0x0FFF) + 2)
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#define CODE_SEG_SIZE(s) ((((s) >> 12) & 0xF) + 3)
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typedef struct {
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u32 off_size_comp; // 0xOOSSSSSS, where O == reverse offset and S == size
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u32 addsize_dec; // decompressed size - compressed size
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} __attribute__((packed)) CodeLzssFooter;
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// see: https://github.com/zoogie/DSP1/blob/master/source/main.c#L44
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u32 DecompressCodeLzss(u8* data_start, u32* code_size, u32 max_size) {
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u8* comp_start = data_start;
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// get footer, fix comp_start offset
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if ((*code_size < sizeof(CodeLzssFooter)) || (*code_size > max_size)) return 1;
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CodeLzssFooter* footer = (CodeLzssFooter*) (void*) (data_start + *code_size - sizeof(CodeLzssFooter));
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if (CODE_COMP_SIZE(footer) <= *code_size) comp_start += *code_size - CODE_COMP_SIZE(footer);
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else return 1;
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// more sanity checks
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if ((CODE_COMP_END(footer) < 0) || (CODE_DEC_SIZE(footer) > max_size))
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return 1; // not reverse LZSS compressed code or too big uncompressed
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// set pointers
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u8* data_end = (u8*) comp_start + CODE_DEC_SIZE(footer);
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u8* ptr_in = (u8*) comp_start + CODE_COMP_END(footer);
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u8* ptr_out = data_end;
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// main decompression loop
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while ((ptr_in > comp_start) && (ptr_out > comp_start)) {
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// sanity check
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if (ptr_out < ptr_in) return 1;
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// read and process control byte
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u8 ctrlbyte = *(--ptr_in);
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for (int i = 7; i >= 0; i--) {
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// end conditions met?
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if ((ptr_in <= comp_start) || (ptr_out <= comp_start))
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break;
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// process control byte
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if ((ctrlbyte >> i) & 0x1) {
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// control bit set, read segment code
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ptr_in -= 2;
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u16 seg_code = getle16(ptr_in);
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if (ptr_in < comp_start) return 1; // corrupted code
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u32 seg_off = CODE_SEG_OFFSET(seg_code);
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u32 seg_len = CODE_SEG_SIZE(seg_code);
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// sanity check for output pointer
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if ((ptr_out - seg_len < comp_start) || (ptr_out + seg_off >= data_end))
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return 1;
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// copy data to the correct place
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for (u32 c = 0; c < seg_len; c++) {
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u8 byte = *(ptr_out + seg_off);
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*(--ptr_out) = byte;
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}
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} else {
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// sanity check for both pointers
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if ((ptr_out == comp_start) || (ptr_in == comp_start))
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return 1;
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// control bit not set, copy byte verbatim
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*(--ptr_out) = *(--ptr_in);
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}
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}
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}
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// check pointers
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if ((ptr_in != comp_start) || (ptr_out != comp_start))
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return 1;
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// all fine if arriving here - return the result
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*code_size = data_end - data_start;
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return 0;
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}
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