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disassembler in function

This commit is contained in:
Brad Grantham 2016-11-07 21:22:08 -08:00
parent e5da87770c
commit 88bcde4977
2 changed files with 107 additions and 0 deletions
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dis6502.cpp Normal file
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#include <cstdio>
#include <string>
using namespace std;
tuple<int, string> disassemble_6502(int address, const unsigned char* buffer)
{
static char cstr[512];
int bytelength;
char *p = cstr;
int currentbyte;
int previousbyte;
int paramcount;
int addrmode;
const char *opcode;
const char *pad;
const char *pre;
const char *post;
// Padding for 1,2 & 3 byte instructions
static const char *padding[3] = {" "," ",""};
// 57 Instructions + Undefined ("???")
static const char *instruction[58] = {
// 0 1 2 3 4 5 6 7 8 9
"ADC","AND","ASL","BCC","BCS","BEQ","BIT","BMI","BNE","BPL", // 0
"BRK","BVC","BVS","CLC","CLD","CLI","CLV","CMP","CPX","CPY", // 1
"DEC","DEX","DEY","EOR","INC","INX","INY","JMP","JSR","LDA", // 2
"LDX","LDY","LSR","NOP","ORA","PHA","PHP","PLA","PLP","ROL", // 3
"ROR","ROT","RTI","RTS","SBC","SEC","SED","SEI","STA","STX", // 4
"STY","TAX","TAY","TSX","TXA","TXS","TYA","???"}; // 5
// This is a lookup of the text formating required for mode output, plus one entry to distinguish relative mode
static const char *modes[9][2]={{"",""},{"#",""},{"",",X"},{"",",Y"},{"(",",X)"},{"(","),Y"},{"(",")"},{"A",""},{"",""}};
// Opcode Properties for 256 opcodes {length_in_bytes, mnemonic_lookup, mode_chars_lookup}
static const int opcode_props[256][3] = {
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
// ******** -------- ******** -------- ******** -------- ******** -------- ******** -------- ******** -------- ******** -------- ******** --------
{1,10,0},{2,34,4},{1,57,0},{1,57,0},{1,57,0},{2,34,0},{2,2,0}, {1,57,0},{1,36,0},{2,34,1},{1,2,7}, {1,57,0},{1,57,0},{3,34,0},{3,2,0}, {1,57,0}, // 0
{2,9,8}, {2,34,5},{1,57,0},{1,57,0},{1,57,0},{2,34,2},{2,2,2}, {1,57,0},{1,13,0},{3,34,3},{1,57,0},{1,57,0},{1,57,0},{3,34,2},{3,2,2}, {1,57,0}, // 1
{3,28,0},{2,1,4}, {1,57,0},{1,57,0},{2,6,0}, {2,1,0}, {2,39,0},{1,57,0},{1,38,0},{2,1,1}, {1,39,7},{1,57,0},{3,6,0}, {3,1,0}, {3,39,0},{1,57,0}, // 2
{2,7,8}, {2,1,5}, {1,57,0},{1,57,0},{1,57,0},{2,1,2}, {2,39,2},{1,57,0},{1,45,0},{3,1,3}, {1,57,0},{1,57,0},{1,57,0},{3,1,2}, {3,39,2},{1,57,0}, // 3
{1,42,0},{2,23,4},{1,57,0},{1,57,0},{1,57,0},{2,23,0},{2,32,0},{1,57,0},{1,35,0},{2,23,1},{1,32,7},{1,57,0},{3,27,0},{3,23,0},{3,32,0},{1,57,0}, // 4
{2,11,8},{2,23,5},{1,57,0},{1,57,0},{1,57,0},{2,23,2},{2,32,2},{1,57,0},{1,15,0},{3,23,3},{1,57,0},{1,57,0},{1,57,0},{3,23,2},{3,32,2},{1,57,0}, // 5
{1,43,0},{2,0,4}, {1,57,0},{1,57,0},{1,57,0},{2,0,0}, {2,40,0},{1,57,0},{1,37,0},{2,0,1}, {1,41,7},{1,57,0},{3,27,6},{3,0,0}, {3,40,0},{1,57,0}, // 6
{2,12,8},{2,0,5}, {1,57,0},{1,57,0},{1,57,0},{2,0,2}, {2,40,2},{1,57,0},{1,47,0},{3,0,3}, {1,57,0},{1,57,0},{1,57,0},{3,0,2}, {3,40,2},{1,57,0}, // 7
{1,57,0},{2,48,4},{1,57,0},{1,57,0},{2,50,0},{2,48,0},{2,49,0},{1,57,0},{1,22,0},{1,57,0},{1,54,0},{1,57,0},{3,50,0},{3,48,0},{3,49,0},{1,57,0}, // 8
{2,3,8}, {2,48,5},{1,57,0},{1,57,0},{2,50,2},{2,48,2},{2,49,3},{1,57,0},{1,56,0},{3,48,3},{1,55,0},{1,57,0},{1,57,0},{3,48,2},{1,57,0},{1,57,0}, // 9
{2,31,1},{2,29,4},{2,30,1},{1,57,0},{2,31,0},{2,29,0},{2,30,0},{1,57,0},{1,52,0},{2,29,1},{1,51,0},{1,57,0},{3,31,0},{3,29,0},{3,30,0},{1,57,0}, // A
{2,4,8}, {2,29,5},{1,57,0},{1,57,0},{2,31,2},{2,29,2},{2,30,3},{1,57,0},{1,16,0},{3,29,3},{1,53,0},{1,57,0},{3,31,2},{3,29,2},{3,30,3},{1,57,0}, // B
{2,19,1},{2,17,4},{1,57,0},{1,57,0},{2,19,0},{2,17,0},{2,20,0},{1,57,0},{1,26,0},{2,17,1},{1,21,0},{1,57,0},{3,19,0},{3,17,0},{3,20,0},{1,57,0}, // C
{2,8,8}, {2,17,5},{1,57,0},{1,57,0},{1,57,0},{2,17,2},{2,20,2},{1,57,0},{1,14,0},{3,17,3},{1,57,0},{1,57,0},{1,57,0},{3,17,2},{3,20,2},{1,57,0}, // D
{2,18,1},{2,44,4},{1,57,0},{1,57,0},{2,18,0},{2,44,0},{2,24,0},{1,57,0},{1,25,0},{2,44,1},{1,33,0},{1,57,0},{3,18,0},{3,44,0},{3,24,0},{1,57,0}, // E
{2,5,8}, {2,44,5},{1,57,0},{1,57,0},{1,57,0},{2,44,2},{2,24,2},{1,57,0},{1,46,0},{3,44,3},{1,57,0},{1,57,0},{1,57,0},{3,44,2},{3,24,2},{1,57,0} // F
};
paramcount = 0;
int stored = 0;
for (int i = 0; i < 4; ++i) { //Start proccessing loop.
previousbyte = currentbyte;
currentbyte = ((unsigned char * ) buffer)[i];
if (paramcount == 0) {
sprintf(p, "%04X %n", address, &stored); //Display current address at beginning of line
p += stored;
paramcount = opcode_props[currentbyte][0]; //Get instruction length
bytelength = 1 + paramcount;
opcode = instruction[opcode_props[currentbyte][1]]; //Get opcode name
addrmode = opcode_props[currentbyte][2]; //Get info required to display addressing mode
pre = modes[addrmode][0]; //Look up pre-operand formatting text
post = modes[addrmode][1]; //Look up post-operand formatting text
pad = padding[(paramcount - 1)]; //Calculate correct padding for output alignment
address = address + paramcount; //Increment address
}
if (paramcount != 0) //Keep track of possition within instruction
paramcount = paramcount - 1;
sprintf(p, "%02X %n", currentbyte, &stored); //Display the current byte in HEX
p += stored;
if (paramcount == 0) {
sprintf(p, " %s %s %s%n", pad, opcode, pre, &stored); //Pad text, display instruction name and pre-operand chars
p += stored;
if (strcmp(pad, " ") == 0) { //Check if single operand instruction
if (addrmode != 8) { //If not using relative addressing ...
sprintf(p, "$%02X%n", currentbyte, &stored); //...display operand
p += stored;
} else { //Addressing mode is relative...
sprintf(p, "$%02X%n", (address + ((currentbyte < 128) ? currentbyte : currentbyte - 256)), &stored); //...display relative address.
p += stored;
}
}
if (strcmp(pad, "") == 0) { //Check if two operand instruction and if so...
sprintf(p, "$%02X%02X%n", currentbyte, previousbyte, &stored); //...display operand
p += stored;
}
sprintf(p, "%s%n", post, &stored); //Display post-operand chars
p += stored;
break;
}
}
return make_tuple(bytelength, string(cstr));
}

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#include <string>
std::tuple<int, std::string> disassemble_6502(int address, const unsigned char* buffer);