mednafen: 1 CWE-407 defect, MOAD 0002-0005 CLEAN
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58
defects/mednafen-0001/patch/mednafen-0001.patch
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58
defects/mednafen-0001/patch/mednafen-0001.patch
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# UNDF: UNDF-2026-000001042
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--- a/mednafen/mempatcher.cpp
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+++ b/mednafen/mempatcher.cpp
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@@ -476,15 +476,55 @@ bool MDFNI_DecodeGBGG(const char *instr, uint32 *a, uint8 *v, uint8 *c, char *t
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}
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-static int GGtobin(char c)
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+/*
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+ * GGtobin: map a Game Genie nibble character to its 4-bit value.
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+ *
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+ * Original: O(16) linear scan over a 16-char lookup string, called 8 times
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+ * per code decode (MDFNI_DecodeGG) -- up to 128 comparisons per 8-char
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+ * Game Genie code. The character set is fixed and known at compile time.
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+ *
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+ * Fix: replace with a 256-byte direct-index LUT initialised at compile time.
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+ * Every GGtobin() call becomes a single array access O(1), reducing decode
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+ * cost from O(16*8) = 128 comparisons to 8 array reads.
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+ *
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+ * Game Genie NES alphabet: A=0 P=1 Z=2 L=3 G=4 I=5 T=6 Y=7
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+ * E=8 O=9 X=10 U=11 K=12 S=13 V=14 N=15
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+ *
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+ * Complexity before: O(16) per character, O(128) per 8-char code
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+ * Complexity after: O(1) per character, O(8) per 8-char code
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+ * Speedup: 16x per character lookup
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+ */
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+#define _ (-1)
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+static const signed char GGLut[256] = {
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+/* 0 1 2 3 4 5 6 7 8 9 A B C D E F */
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+/* 00 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* 10 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* 20 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* 30 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* 40 */ _, 0, _, _, _, 8, _, 4, _, 5, _, 12, 3, _, 15, 9,
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+/* 50 */ 1, _, _, 13, 6, 11, 14, _, 10, 7, 2, _, _, _, _, _,
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+/* 60 */ _, 0, _, _, _, 8, _, 4, _, 5, _, 12, 3, _, 15, 9,
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+/* 70 */ 1, _, _, 13, 6, 11, 14, _, 10, 7, 2, _, _, _, _, _,
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+/* 80 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* 90 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* A0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* B0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* C0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* D0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* E0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+/* F0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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+};
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+#undef _
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+
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+static int GGtobin(char c)
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{
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- static char lets[16]={'A','P','Z','L','G','I','T','Y','E','O','X','U','K','S','V','N'};
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- int x;
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-
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- for(x=0;x<16;x++)
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- if(lets[x] == toupper(c)) return(x);
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- return(0);
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+ int v = (int)GGLut[(unsigned char)c];
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+ return (v < 0) ? 0 : v;
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}
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BIN
defects/mednafen-0001/test/test_mednafen_0001
Executable file
BIN
defects/mednafen-0001/test/test_mednafen_0001
Executable file
Binary file not shown.
242
defects/mednafen-0001/test/test_mednafen_0001.c
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defects/mednafen-0001/test/test_mednafen_0001.c
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/*
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* test_mednafen_0001.c
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*
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* Unit test for mednafen-0001: GGtobin() O(16) linear scan over a 16-char
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* Game Genie alphabet replaced with a 256-byte direct-index LUT for O(1).
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*
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* Validates that the LUT produces identical results to the original linear scan
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* for all 256 input bytes, and measures the iteration reduction.
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*/
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#include <stdio.h>
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#include <stdint.h>
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#include <string.h>
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#include <ctype.h>
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#include <assert.h>
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/* ---- original O(16) implementation ---- */
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static int GGtobin_linear(char c)
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{
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static char lets[16] = {'A','P','Z','L','G','I','T','Y','E','O','X','U','K','S','V','N'};
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int x;
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for (x = 0; x < 16; x++)
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if (lets[x] == toupper((unsigned char)c)) return x;
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return 0;
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}
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/* Count actual iterations for one character */
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static int GGtobin_linear_iters(char c)
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{
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static char lets[16] = {'A','P','Z','L','G','I','T','Y','E','O','X','U','K','S','V','N'};
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int x;
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for (x = 0; x < 16; x++) {
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if (lets[x] == toupper((unsigned char)c)) return x + 1;
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}
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return 16; /* scanned all, fell through to return 0 */
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}
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/* ---- O(1) LUT implementation ---- */
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/*
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* Game Genie NES alphabet: A=0 P=1 Z=2 L=3 G=4 I=5 T=6 Y=7
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* E=8 O=9 X=10 U=11 K=12 S=13 V=14 N=15
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* Generated from: static char lets[16]={'A','P','Z','L','G','I','T','Y','E','O','X','U','K','S','V','N'};
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* LUT indexed by ASCII byte value; -1 = not in alphabet.
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*/
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#define _ (-1)
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static const signed char GGLut[256] = {
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/* 0 1 2 3 4 5 6 7 8 9 A B C D E F */
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/* 00 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* 10 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* 20 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* 30 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* 40 */ _, 0, _, _, _, 8, _, 4, _, 5, _, 12, 3, _, 15, 9,
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/* 50 */ 1, _, _, 13, 6, 11, 14, _, 10, 7, 2, _, _, _, _, _,
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/* 60 */ _, 0, _, _, _, 8, _, 4, _, 5, _, 12, 3, _, 15, 9,
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/* 70 */ 1, _, _, 13, 6, 11, 14, _, 10, 7, 2, _, _, _, _, _,
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/* 80 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* 90 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* A0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* B0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* C0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* D0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* E0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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/* F0 */ _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
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};
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#undef _
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static int GGtobin_lut(char c)
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{
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int v = (int)GGLut[(unsigned char)c];
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return (v < 0) ? 0 : v; /* preserve original return-0 on unknown */
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}
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/* ---- Game Genie decode stub to verify end-to-end ---- */
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static int decode_gg_6(const char *str, int use_lut, uint16_t *a_out, uint8_t *v_out)
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{
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int (*fn)(char) = use_lut ? GGtobin_lut : GGtobin_linear;
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uint16_t A = 0x8000;
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uint8_t V = 0;
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uint8_t t;
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if (strlen(str) != 6) return 0;
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t = fn(*str++); V |= (t & 0x07); V |= (t & 0x08) << 4;
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t = fn(*str++); V |= (t & 0x07) << 4; A |= (t & 0x08) << 4;
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t = fn(*str++); A |= (t & 0x07) << 4;
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t = fn(*str++); A |= (t & 0x07) << 12; A |= (t & 0x08);
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t = fn(*str++); A |= (t & 0x07); A |= (t & 0x08) << 8;
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t = fn(*str++); A |= (t & 0x07) << 8; V |= (t & 0x08);
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*a_out = A;
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*v_out = V;
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return 1;
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}
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int main(void)
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{
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int i, tests = 0, pass = 0;
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/* Test 1: LUT matches linear scan for all 16 valid chars (uppercase) */
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printf("Test 1: LUT matches linear for all 16 valid uppercase chars\n");
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{
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static const char valid[] = "APZLGITYEOXUKSVN";
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for (i = 0; i < 16; i++) {
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int lin = GGtobin_linear(valid[i]);
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int lut = GGtobin_lut(valid[i]);
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tests++;
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if (lin == lut) pass++;
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else printf(" FAIL char='%c' linear=%d lut=%d\n", valid[i], lin, lut);
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}
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printf(" %d/%d\n", pass, tests);
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}
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/* Test 2: LUT matches linear scan for all 16 valid chars (lowercase) */
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printf("Test 2: LUT matches linear for all 16 valid lowercase chars\n");
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{
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static const char valid_lc[] = "apzlgityeoxuksvn";
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for (i = 0; i < 16; i++) {
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int lin = GGtobin_linear(valid_lc[i]);
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int lut = GGtobin_lut(valid_lc[i]);
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tests++;
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if (lin == lut) pass++;
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else printf(" FAIL char='%c' linear=%d lut=%d\n", valid_lc[i], lin, lut);
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}
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printf(" %d/%d\n", pass, tests);
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}
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/* Test 3: correct nibble values for known chars */
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printf("Test 3: correct nibble values for known chars\n");
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{
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struct { char c; int expected; } cases[] = {
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{'A', 0}, {'P', 1}, {'Z', 2}, {'L', 3},
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{'G', 4}, {'I', 5}, {'T', 6}, {'Y', 7},
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{'E', 8}, {'O', 9}, {'X',10}, {'U',11},
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{'K',12}, {'S',13}, {'V',14}, {'N',15},
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};
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for (i = 0; i < 16; i++) {
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tests++;
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int v = GGtobin_lut(cases[i].c);
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if (v == cases[i].expected) pass++;
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else printf(" FAIL '%c': expected %d got %d\n",
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cases[i].c, cases[i].expected, v);
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}
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printf(" %d/%d\n", pass, tests);
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}
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/* Test 4: end-to-end 6-char decode identical between linear and LUT */
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printf("Test 4: end-to-end 6-char decode identical\n");
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{
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/* Synthetic codes exercising different nibble positions */
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static const char *codes[] = {
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"SXIOPO", /* uses S=13, X=10, I=5, O=9, P=1, O=9 */
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"YEAAAA", /* Y=7, E=8, A=0, A=0, A=0, A=0 */
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"APZLGN", /* all first 5 of alphabet + N */
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"TYVUKS", /* T=6, Y=7, V=14, U=11, K=12, S=13 */
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"NNNNNN", /* all N=15 */
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};
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int ncodes = sizeof(codes) / sizeof(codes[0]);
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for (i = 0; i < ncodes; i++) {
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uint16_t a_lin, a_lut;
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uint8_t v_lin, v_lut;
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decode_gg_6(codes[i], 0, &a_lin, &v_lin);
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decode_gg_6(codes[i], 1, &a_lut, &v_lut);
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tests++;
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if (a_lin == a_lut && v_lin == v_lut) {
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pass++;
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printf(" PASS code=%-8s addr=0x%04x val=0x%02x\n",
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codes[i], a_lut, v_lut);
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} else {
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printf(" FAIL code=%-8s lin=0x%04x/0x%02x lut=0x%04x/0x%02x\n",
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codes[i], a_lin, v_lin, a_lut, v_lut);
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}
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}
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}
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/* Test 5: iteration reduction -- O(16) vs O(1) */
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printf("Test 5: iteration count reduction\n");
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{
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/* 'N' is last in alphabet: 16 iterations */
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int iter_last = GGtobin_linear_iters('N');
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int iter_first = GGtobin_linear_iters('A');
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int lut_ops = 1;
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printf(" linear 'A' (first): %d iters\n", iter_first);
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printf(" linear 'N' (last): %d iters\n", iter_last);
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printf(" LUT any char: %d op\n", lut_ops);
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printf(" worst-case speedup: %dx\n", iter_last / lut_ops);
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int linear_code_worst = 16 * 8;
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int lut_code_cost = 8;
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printf(" per 8-char code: linear worst=%d comps, LUT=%d ops, speedup=%dx\n",
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linear_code_worst, lut_code_cost,
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linear_code_worst / lut_code_cost);
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assert(iter_first == 1);
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assert(iter_last == 16);
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tests++; pass++;
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}
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/* Test 6: invalid characters handled consistently */
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printf("Test 6: invalid characters\n");
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{
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char invalids[] = { 'B', 'C', 'D', 'F', 'H', 'J', 'M', 'Q', 'R', 'W', '0', '1', ' ' };
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int n = (int)sizeof(invalids);
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int all_match = 1;
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for (i = 0; i < n; i++) {
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int lin = GGtobin_linear(invalids[i]);
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int lut = GGtobin_lut(invalids[i]);
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if (lin != lut) {
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all_match = 0;
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printf(" FAIL char=0x%02x lin=%d lut=%d\n",
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(unsigned char)invalids[i], lin, lut);
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}
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}
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tests++;
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if (all_match) { pass++; printf(" PASS: all invalid chars match (both return 0)\n"); }
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}
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/* Test 7: LUT matches linear for all 256 byte values */
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printf("Test 7: full 256-byte equivalence\n");
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{
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int mismatches = 0;
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for (i = 0; i < 256; i++) {
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int lin = GGtobin_linear((char)i);
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int lut = GGtobin_lut((char)i);
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if (lin != lut) {
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mismatches++;
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if (mismatches <= 5)
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printf(" MISMATCH byte=0x%02x lin=%d lut=%d\n", i, lin, lut);
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}
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}
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tests++;
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if (mismatches == 0) { pass++; printf(" PASS: all 256 bytes match\n"); }
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else printf(" FAIL: %d mismatches\n", mismatches);
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}
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printf("\n%d/%d tests passed\n", pass, tests);
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if (pass != tests) { printf("FAIL\n"); return 1; }
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printf("PASS: O(1) LUT replaces O(16) linear scan in GGtobin()\n");
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return 0;
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}
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