Add string encoding option (#133)

* Update compiler-utils.js

Customizable string encoding

* implement string encoding option

* accept no args for cstring

Author: extremeheat

src/datatypes/compiler-utils.js

@@ -14,7 +14,7 @@ module.exports = {
       code += 'if (offset + count > buffer.length) {\n'
       code += '  throw new PartialReadError("Missing characters in string, found size is " + buffer.length + " expected size was " + (offset + count))\n'
       code += '}\n'
-      code += 'return { value: buffer.toString(\'utf8\', offset, offset + count), size: count + countSize }'
+      code += `return { value: buffer.toString("${string.encoding || 'utf8'}", offset, offset + count), size: count + countSize }`
       return compiler.wrapCode(code)
     }],
     buffer: ['parametrizable', (compiler, buffer) => {
@@ -67,13 +67,13 @@ module.exports = {
 
   Write: {
     pstring: ['parametrizable', (compiler, string) => {
-      let code = 'const length = Buffer.byteLength(value, \'utf8\')\n'
+      let code = `const length = Buffer.byteLength(value, "${string.encoding || 'utf8'}")\n`
       if (string.countType) {
         code += 'offset = ' + compiler.callType('length', string.countType) + '\n'
       } else if (string.count === null) {
         throw new Error('pstring must contain either count or countType')
       }
-      code += 'buffer.write(value, offset, length, \'utf8\')\n'
+      code += `buffer.write(value, offset, length, "${string.encoding || 'utf8'}")\n`
       code += 'return offset + length'
       return compiler.wrapCode(code)
     }],
@@ -125,7 +125,7 @@ module.exports = {
 
   SizeOf: {
     pstring: ['parametrizable', (compiler, string) => {
-      let code = 'let size = Buffer.byteLength(value, \'utf8\')\n'
+      let code = `let size = Buffer.byteLength(value, "${string.encoding || 'utf8'}")\n`
       if (string.countType) {
         code += 'size += ' + compiler.callType('size', string.countType) + '\n'
       } else if (string.count === null) {

src/datatypes/utils.js

@@ -111,20 +111,20 @@ function readPString (buffer, offset, typeArgs, rootNode) {
   }
 
   return {
-    value: buffer.toString('utf8', cursor, strEnd),
+    value: buffer.toString(typeArgs.encoding || 'utf8', cursor, strEnd),
     size: strEnd - offset
   }
 }
 
 function writePString (value, buffer, offset, typeArgs, rootNode) {
   const length = Buffer.byteLength(value, 'utf8')
   offset = sendCount.call(this, length, buffer, offset, typeArgs, rootNode)
-  buffer.write(value, offset, length, 'utf8')
+  buffer.write(value, offset, length, typeArgs.encoding || 'utf8')
   return offset + length
 }
 
 function sizeOfPString (value, typeArgs, rootNode) {
-  const length = Buffer.byteLength(value, 'utf8')
+  const length = Buffer.byteLength(value, typeArgs.encoding || 'utf8')
   const size = calcCount.call(this, length, typeArgs, rootNode)
   return size + length
 }
@@ -237,20 +237,20 @@ function sizeOfBitField (value, typeArgs) {
   }, 0) / 8)
 }
 
-function readCString (buffer, offset) {
+function readCString (buffer, offset, typeArgs) {
   let size = 0
   while (offset + size < buffer.length && buffer[offset + size] !== 0x00) { size++ }
   if (buffer.length < offset + size + 1) { throw new PartialReadError() }
 
   return {
-    value: buffer.toString('utf8', offset, offset + size),
+    value: buffer.toString(typeArgs?.encoding || 'utf8', offset, offset + size),
     size: size + 1
   }
 }
 
-function writeCString (value, buffer, offset) {
-  const length = Buffer.byteLength(value, 'utf8')
-  buffer.write(value, offset, length, 'utf8')
+function writeCString (value, buffer, offset, typeArgs) {
+  const length = Buffer.byteLength(value, typeArgs?.encoding || 'utf8')
+  buffer.write(value, offset, length, typeArgs?.encoding || 'utf8')
   offset += length
   buffer.writeInt8(0x00, offset)
   return offset + 1