Turns out some string pools can refer to the same string multiple tim…

…es. Previously we attempted to load as many individual strings as the pool had items. Now we're using the provided offsets. Fixes #17.

lib/apkreader/parser/binaryxml.js

@@ -2,6 +2,7 @@
 
 // Heavily inspired by https://github.com/xiaxiaocao/apk-parser
 
+const assert = require('assert')
 const debug = require('debug')('adb:apkreader:parser:binaryxml')
 
 const NodeType = {
@@ -306,13 +307,13 @@ and is supposed to end at offset ${end}. Ignoring the rest of the value.`)
       var stringLength = this.readLength8(encoding)
       var byteLength = this.readLength8(encoding)
       var value = this.buffer.toString(encoding, this.cursor, (this.cursor += byteLength))
-      this.readU8() // Trailing zero
+      assert.equal(this.readU8(), 0, 'String must end with trailing zero')
       return value
     case 'ucs2':
       stringLength = this.readLength16(encoding)
       byteLength = stringLength * 2
       value = this.buffer.toString(encoding, this.cursor, (this.cursor += byteLength))
-      this.readU16() // Trailing zero
+      assert.equal(this.readU16(), 0, 'String must end with trailing zero')
       return value
     default:
       throw new Error(`Unsupported encoding '${encoding}'`)
@@ -321,6 +322,7 @@ and is supposed to end at offset ${end}. Ignoring the rest of the value.`)
 
   readChunkHeader() {
     return {
+      startOffset: this.cursor,
       chunkType: this.readU16(),
       headerSize: this.readU16(),
       chunkSize: this.readU32()
@@ -338,8 +340,6 @@ and is supposed to end at offset ${end}. Ignoring the rest of the value.`)
       throw new Error('Invalid string pool header')
     }
 
-    const anchor = this.cursor
-
     const offsets = []
     for (let i = 0, l = header.stringCount; i < l; ++i) {
       offsets.push(this.readU32())
@@ -350,13 +350,15 @@ and is supposed to end at offset ${end}. Ignoring the rest of the value.`)
       ? 'utf-8'
       : 'ucs2'
 
-    this.cursor = (anchor + header.stringsStart) - header.headerSize
+    const stringsStart = header.startOffset + header.stringsStart
+    this.cursor = stringsStart
     for (let i = 0, l = header.stringCount; i < l; ++i) {
+      this.cursor = stringsStart + offsets[i]
       this.strings.push(this.readString(encoding))
     }
 
     // Skip styles
-    this.cursor = (anchor + header.chunkSize) - header.headerSize
+    this.cursor = header.startOffset + header.chunkSize
 
     return null
   }