From ab1ec89f22808c38426f7e0d4e4f0e1a5bc3aec9 Mon Sep 17 00:00:00 2001
From: Random <28494085+Random06457@users.noreply.github.com>
Date: Mon, 22 Jun 2020 00:43:14 +0200
Subject: Decompile jpegdecoder.c, padsetup.c and code_800C3C20.c (#217)

* Decompile jpegdecoder.c, padsetup.c and code_800C3C20.c

* change func_800C3C20's prototype and rename some fields in jpeg related structs

* Fix comment in Jpeg_GetU16 and change func_800C3C20

* use a switch in padsetup.c
---
 src/code/jpegdecoder.c | 201 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 201 insertions(+)
 create mode 100644 src/code/jpegdecoder.c

(limited to 'src/code/jpegdecoder.c')

diff --git a/src/code/jpegdecoder.c b/src/code/jpegdecoder.c
new file mode 100644
index 000000000..1f73a4626
--- /dev/null
+++ b/src/code/jpegdecoder.c
@@ -0,0 +1,201 @@
+#include <global.h>
+
+u8* sJpegBitStreamPtr;
+u32 sJpegBitStreamByteIdx;
+u8 sJpegBitStreamBitIdx;
+u8 sJpegBitStreamDontSkip;
+u32 sJpegBitStreamCurWord;
+
+s32 JpegDecoder_Decode(JpegDecoder* decoder, u16* mcuBuff, s32 count, u8 isFollowing, JpegDecoderState* state) {
+    s16 pad;
+    s16 unk0;
+    s16 unk1;
+    s16 unk2;
+    u32 idx;
+    s32 inc;
+    s16 unkCount;
+
+    JpegHuffmanTable* hTable0;
+    JpegHuffmanTable* hTable1;
+    JpegHuffmanTable* hTable2;
+    JpegHuffmanTable* hTable3;
+
+    inc = 0;
+    sJpegBitStreamPtr = decoder->imageData;
+    if (decoder->mode == 0) {
+        unkCount = 2;
+    } else {
+        unkCount = 4;
+        if (decoder->unk_05 == 1) {
+            inc = 8 * 8 * 2;
+        }
+    }
+
+    hTable0 = decoder->hTablePtrs[0];
+    hTable1 = decoder->hTablePtrs[1];
+    hTable2 = decoder->hTablePtrs[2];
+    hTable3 = decoder->hTablePtrs[3];
+
+    if (!isFollowing) {
+        sJpegBitStreamByteIdx = 0;
+        sJpegBitStreamBitIdx = 32;
+        sJpegBitStreamCurWord = 0;
+        sJpegBitStreamDontSkip = 0;
+        unk0 = 0;
+        unk1 = 0;
+        unk2 = 0;
+    } else {
+        sJpegBitStreamByteIdx = state->byteIdx;
+        sJpegBitStreamBitIdx = state->bitIdx;
+        sJpegBitStreamCurWord = state->curWord;
+        sJpegBitStreamDontSkip = state->dontSkip;
+        unk0 = state->unk_0C;
+        unk1 = state->unk_0E;
+        unk2 = state->unk_10;
+    }
+
+    while (count != 0) {
+        for (idx = 0; idx < unkCount; idx++) {
+            if (JpegDecoder_ProcessMcu(hTable0, hTable1, mcuBuff, &unk0)) {
+                return 2;
+            }
+            mcuBuff += 8 * 8;
+        }
+
+        if (JpegDecoder_ProcessMcu(hTable2, hTable3, mcuBuff, &unk1)) {
+            return 2;
+        }
+        mcuBuff += 8 * 8;
+
+        if (JpegDecoder_ProcessMcu(hTable2, hTable3, mcuBuff, &unk2)) {
+            return 2;
+        }
+
+        count--;
+        mcuBuff += 8 * 8;
+        mcuBuff += inc;
+    }
+
+    state->byteIdx = sJpegBitStreamByteIdx;
+    state->bitIdx = sJpegBitStreamBitIdx;
+    state->curWord = sJpegBitStreamCurWord;
+    state->dontSkip = sJpegBitStreamDontSkip;
+    state->unk_0C = unk0;
+    state->unk_0E = unk1;
+    state->unk_10 = unk2;
+    return 0;
+}
+
+s32 JpegDecoder_ProcessMcu(JpegHuffmanTable* hTable0, JpegHuffmanTable* hTable1, s16* mcu, s16* unk) {
+    s8 i = 0;
+    s8 zeroCount;
+    s16 coeff;
+
+    if (JpegDecoder_ParseNextSymbol(hTable0, &coeff, &zeroCount)) {
+        return 1;
+    }
+
+    *unk += coeff;
+    mcu[i++] = *unk;
+    while (i < 8 * 8) {
+        if (JpegDecoder_ParseNextSymbol(hTable1, &coeff, &zeroCount) != 0) {
+            return 1;
+        }
+
+        if (coeff == 0) {
+            if (zeroCount == 0xF) {
+                while (zeroCount-- >= 0) {
+                    mcu[i++] = 0;
+                }
+            } else {
+                while (i < 8 * 8) {
+                    mcu[i++] = 0;
+                }
+                break;
+            }
+        } else {
+            while (0 < zeroCount--) {
+                mcu[i++] = 0;
+            }
+            mcu[i++] = coeff;
+        }
+    }
+
+    return 0;
+}
+
+#ifdef NON_MATCHING
+// stack usage (coeffLength is stored as a u32 instead of a u8)
+s32 JpegDecoder_ParseNextSymbol(JpegHuffmanTable* hTable, s16* outCoeff, u8* outZeroCount) {
+    u16 buff;
+    u8 codeIdx;
+    u8 sym;
+    u8 coeffLength; // 0x26
+    u16 codeOff;    // 0x24
+
+    codeOff = 0;
+    buff = JpegDecoder_ReadBits(16);
+
+    for (codeIdx = 0; codeIdx < 16; codeIdx++) {
+        if (hTable->codesB[codeIdx] == 0xFFFF) {
+            continue;
+        }
+
+        codeOff = buff >> (15 - codeIdx);
+        if (codeOff <= hTable->codesB[codeIdx]) {
+            break;
+        }
+    }
+
+    if (codeIdx >= 16) {
+        return 1;
+    }
+
+    sym = hTable->symbols[hTable->codeOffs[codeIdx] + codeOff - hTable->codesA[codeIdx]];
+    *outZeroCount = sym >> 4;
+    coeffLength = sym & 0xF; // not using a temp for "sym & 0xF" puts coeffLength on the stack
+
+    sJpegBitStreamBitIdx += codeIdx - 15;
+    *outCoeff = 0;
+    if (coeffLength) { // (cond != 0) instead of (cond) puts coeffLength on the stack
+        *outCoeff = JpegDecoder_ReadBits(coeffLength);
+        if (*outCoeff < (1 << (coeffLength - 1))) {
+            *outCoeff +=
+                (-1 << coeffLength) + 1; // (*outCoeff -= (1 << coeffLength)-1; makes more sense but doesn't match)
+        }
+    }
+
+    return 0;
+}
+#else
+#pragma GLOBAL_ASM("asm/non_matchings/code/jpegdecoder/JpegDecoder_ParseNextSymbol.s")
+#endif
+
+u16 JpegDecoder_ReadBits(u8 len) {
+    u8 byteCount;
+    u8 data;
+    s32 ret;
+    u32 temp;
+    ret = 0; // this is required for some reason
+
+    for (byteCount = sJpegBitStreamBitIdx >> 3; byteCount > 0; byteCount--) {
+        data = sJpegBitStreamPtr[sJpegBitStreamByteIdx++];
+        if (sJpegBitStreamDontSkip) {
+            if (data == 0) {
+                data = sJpegBitStreamPtr[sJpegBitStreamByteIdx++];
+            }
+        }
+
+        sJpegBitStreamDontSkip = (data == 0xFF) ? 1 : 0;
+
+        sJpegBitStreamCurWord <<= 8;
+        sJpegBitStreamCurWord |= data;
+        sJpegBitStreamBitIdx -= 8;
+    }
+
+    ret = (sJpegBitStreamCurWord << (sJpegBitStreamBitIdx));
+    temp = ret;
+    ret = temp >> -len;
+    sJpegBitStreamBitIdx += len;
+    return ret;
+}
-- 
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