pngjs/lib/sync-inflate.js

"use strict";

let assert = require("assert").ok;
let zlib = require("zlib");
let util = require("util");

let kMaxLength = require("buffer").kMaxLength;

function Inflate(opts) {
  if (!(this instanceof Inflate)) {
    return new Inflate(opts);
  }

  if (opts && opts.chunkSize < zlib.Z_MIN_CHUNK) {
    opts.chunkSize = zlib.Z_MIN_CHUNK;
  }

  zlib.Inflate.call(this, opts);

  // Node 8 --> 9 compatibility check
  this._offset = this._offset === undefined ? this._outOffset : this._offset;
  this._buffer = this._buffer || this._outBuffer;

  if (opts && opts.maxLength != null) {
    this._maxLength = opts.maxLength;
  }
}

function createInflate(opts) {
  return new Inflate(opts);
}

function _close(engine, callback) {
  if (callback) {
    process.nextTick(callback);
  }

  // Caller may invoke .close after a zlib error (which will null _handle).
  if (!engine._handle) {
    return;
  }

  engine._handle.close();
  engine._handle = null;
}

Inflate.prototype._processChunk = function (chunk, flushFlag, asyncCb) {
  if (typeof asyncCb === "function") {
    return zlib.Inflate._processChunk.call(this, chunk, flushFlag, asyncCb);
  }

  let self = this;

  let availInBefore = chunk && chunk.length;
  let availOutBefore = this._chunkSize - this._offset;
  let leftToInflate = this._maxLength;
  let inOff = 0;

  let buffers = [];
  let nread = 0;

  let error;
  this.on("error", function (err) {
    error = err;
  });

  function handleChunk(availInAfter, availOutAfter) {
    if (self._hadError) {
      return;
    }

    let have = availOutBefore - availOutAfter;
    assert(have >= 0, "have should not go down");

    if (have > 0) {
      let out = self._buffer.slice(self._offset, self._offset + have);
      self._offset += have;

      if (out.length > leftToInflate) {
        out = out.slice(0, leftToInflate);
      }

      buffers.push(out);
      nread += out.length;
      leftToInflate -= out.length;

      if (leftToInflate === 0) {
        return false;
      }
    }

    if (availOutAfter === 0 || self._offset >= self._chunkSize) {
      availOutBefore = self._chunkSize;
      self._offset = 0;
      self._buffer = Buffer.allocUnsafe(self._chunkSize);
    }

    if (availOutAfter === 0) {
      inOff += availInBefore - availInAfter;
      availInBefore = availInAfter;

      return true;
    }

    return false;
  }

  assert(this._handle, "zlib binding closed");
  let res;
  do {
    res = this._handle.writeSync(
      flushFlag,
      chunk, // in
      inOff, // in_off
      availInBefore, // in_len
      this._buffer, // out
      this._offset, //out_off
      availOutBefore
    ); // out_len
    // Node 8 --> 9 compatibility check
    res = res || this._writeState;
  } while (!this._hadError && handleChunk(res[0], res[1]));

  if (this._hadError) {
    throw error;
  }

  if (nread >= kMaxLength) {
    _close(this);
    throw new RangeError(
      "Cannot create final Buffer. It would be larger than 0x" +
        kMaxLength.toString(16) +
        " bytes"
    );
  }

  let buf = Buffer.concat(buffers, nread);
  _close(this);

  return buf;
};

util.inherits(Inflate, zlib.Inflate);

function zlibBufferSync(engine, buffer) {
  if (typeof buffer === "string") {
    buffer = Buffer.from(buffer);
  }
  if (!(buffer instanceof Buffer)) {
    throw new TypeError("Not a string or buffer");
  }

  let flushFlag = engine._finishFlushFlag;
  if (flushFlag == null) {
    flushFlag = zlib.Z_FINISH;
  }

  return engine._processChunk(buffer, flushFlag);
}

function inflateSync(buffer, opts) {
  return zlibBufferSync(new Inflate(opts), buffer);
}

module.exports = exports = inflateSync;
exports.Inflate = Inflate;
exports.createInflate = createInflate;
exports.inflateSync = inflateSync;