src/v5/inputSource/StringSource.js
const whiteSpaces = [" ", "\n", "\t"];
class StringSource{
constructor(str){
this.line = 1;
this.cols = 0;
this.buffer = str;
//a boundary pointer to indicate where from the buffer dat should be read
// data before this pointer can be deleted to free the memory
this.startIndex = 0;
}
readCh() {
return this.buffer[this.startIndex++];
}
readChAt(index) {
return this.buffer[this.startIndex+index];
}
readStr(n,from){
if(typeof from === "undefined") from = this.startIndex;
return this.buffer.substring(from, from + n);
}
readUpto(stopStr) {
const inputLength = this.buffer.length;
const stopLength = stopStr.length;
for (let i = this.startIndex; i < inputLength; i++) {
let match = true;
for (let j = 0; j < stopLength; j++) {
if (this.buffer[i + j] !== stopStr[j]) {
match = false;
break;
}
}
if (match) {
const result = this.buffer.substring(this.startIndex, i);
this.startIndex = i + stopLength;
return result;
}
}
throw new Error(`Unexpected end of source. Reading '${stopStr}'`);
}
readUptoCloseTag(stopStr) { //stopStr: "</tagname"
const inputLength = this.buffer.length;
const stopLength = stopStr.length;
let stopIndex = 0;
//0: non-matching, 1: matching stop string, 2: matching closing
let match = 0;
for (let i = this.startIndex; i < inputLength; i++) {
if(match === 1){//initial part matched
if(stopIndex === 0) stopIndex = i;
if(this.buffer[i] === ' ' || this.buffer[i] === '\t') continue;
else if(this.buffer[i] === '>'){
match = 2;
//tag boundary found
// this.startIndex
}
}else{
match = 1;
for (let j = 0; j < stopLength; j++) {
if (this.buffer[i + j] !== stopStr[j]) {
match = 0;
break;
}
}
}
if (match === 2) {//matched closing part
const result = this.buffer.substring(this.startIndex, stopIndex - 1 );
this.startIndex = i + 1;
return result;
}
}
throw new Error(`Unexpected end of source. Reading '${stopStr}'`);
}
readFromBuffer(n, updateIndex){
let ch;
if(n===1){
ch = this.buffer[this.startIndex];
// if(ch === "\n") {
// this.line++;
// this.cols = 1;
// }else{
// this.cols++;
// }
}else{
ch = this.buffer.substring(this.startIndex, this.startIndex + n);
// if("".indexOf("\n") !== -1){
// //TODO: handle the scenario when there are multiple lines
// //TODO: col should be set to number of chars after last '\n'
// // this.cols = 1;
// }else{
// this.cols += n;
// }
}
if(updateIndex) this.updateBufferBoundary(n);
return ch;
}
//TODO: rename to updateBufferReadIndex
updateBufferBoundary(n = 1) { //n: number of characters read
this.startIndex += n;
}
canRead(n){
n = n || this.startIndex;
return this.buffer.length - n + 1 > 0;
}
}
module.exports = StringSource;