Additional tools for debugging v86 programs

v86_debug_tools.js

// Searches memory for specific sequence represented by string
//  want = desired string sequence
//  buf = memory buffer
//  skip = spacing between each consequtive element of the sequence in the buf to find
function find_str_in_mem(want, buf, skip) {
  skip = skip || 1;
  var wantbuf = new Uint8Array(want.length);
  for (let i = 0; i < want.length; i++) {
    wantbuf[i] = want.charCodeAt(i);
  }
  var found = [];
  for (let k = 0; k < buf.length; k += 0x1000000) {
    console.log('                  Entering ' + h(k));
    for (let i = k; i < buf.length && i < k + 0x1000000; i++) {
        if (wantbuf[0] !== buf[i]) continue;
        for (let j = 0; j < want.length; j++) {
          if (wantbuf[j] !== buf[i + j * skip]) break;
          if (j + 1 === want.length) {
            found.push(i);
            console.log('Found at ' + h(i));
          }
        }
    }
  }
  return found;
}

// Looks at the ansi string representation of a block of memory
function inspect_mem(location, size) {
  size = size || 2048;
  return cpu.mem8.subarray(location, location + size).reduce((a,v) => a + String.fromCharCode(v), '');
}