planning

node_modules/geotiff/dist-module/dataslice.js

@@ -0,0 +1,140 @@
+export default class DataSlice {
+  constructor(arrayBuffer, sliceOffset, littleEndian, bigTiff) {
+    this._dataView = new DataView(arrayBuffer);
+    this._sliceOffset = sliceOffset;
+    this._littleEndian = littleEndian;
+    this._bigTiff = bigTiff;
+  }
+
+  get sliceOffset() {
+    return this._sliceOffset;
+  }
+
+  get sliceTop() {
+    return this._sliceOffset + this.buffer.byteLength;
+  }
+
+  get littleEndian() {
+    return this._littleEndian;
+  }
+
+  get bigTiff() {
+    return this._bigTiff;
+  }
+
+  get buffer() {
+    return this._dataView.buffer;
+  }
+
+  covers(offset, length) {
+    return this.sliceOffset <= offset && this.sliceTop >= offset + length;
+  }
+
+  readUint8(offset) {
+    return this._dataView.getUint8(
+      offset - this._sliceOffset, this._littleEndian,
+    );
+  }
+
+  readInt8(offset) {
+    return this._dataView.getInt8(
+      offset - this._sliceOffset, this._littleEndian,
+    );
+  }
+
+  readUint16(offset) {
+    return this._dataView.getUint16(
+      offset - this._sliceOffset, this._littleEndian,
+    );
+  }
+
+  readInt16(offset) {
+    return this._dataView.getInt16(
+      offset - this._sliceOffset, this._littleEndian,
+    );
+  }
+
+  readUint32(offset) {
+    return this._dataView.getUint32(
+      offset - this._sliceOffset, this._littleEndian,
+    );
+  }
+
+  readInt32(offset) {
+    return this._dataView.getInt32(
+      offset - this._sliceOffset, this._littleEndian,
+    );
+  }
+
+  readFloat32(offset) {
+    return this._dataView.getFloat32(
+      offset - this._sliceOffset, this._littleEndian,
+    );
+  }
+
+  readFloat64(offset) {
+    return this._dataView.getFloat64(
+      offset - this._sliceOffset, this._littleEndian,
+    );
+  }
+
+  readUint64(offset) {
+    const left = this.readUint32(offset);
+    const right = this.readUint32(offset + 4);
+    let combined;
+    if (this._littleEndian) {
+      combined = left + ((2 ** 32) * right);
+      if (!Number.isSafeInteger(combined)) {
+        throw new Error(
+          `${combined} exceeds MAX_SAFE_INTEGER. `
+          + 'Precision may be lost. Please report if you get this message to https://github.com/geotiffjs/geotiff.js/issues',
+        );
+      }
+      return combined;
+    }
+    combined = ((2 ** 32) * left) + right;
+    if (!Number.isSafeInteger(combined)) {
+      throw new Error(
+        `${combined} exceeds MAX_SAFE_INTEGER. `
+        + 'Precision may be lost. Please report if you get this message to https://github.com/geotiffjs/geotiff.js/issues',
+      );
+    }
+
+    return combined;
+  }
+
+  // adapted from https://stackoverflow.com/a/55338384/8060591
+  readInt64(offset) {
+    let value = 0;
+    const isNegative = (this._dataView.getUint8(offset + (this._littleEndian ? 7 : 0)) & 0x80)
+      > 0;
+    let carrying = true;
+    for (let i = 0; i < 8; i++) {
+      let byte = this._dataView.getUint8(
+        offset + (this._littleEndian ? i : 7 - i),
+      );
+      if (isNegative) {
+        if (carrying) {
+          if (byte !== 0x00) {
+            byte = ~(byte - 1) & 0xff;
+            carrying = false;
+          }
+        } else {
+          byte = ~byte & 0xff;
+        }
+      }
+      value += byte * (256 ** i);
+    }
+    if (isNegative) {
+      value = -value;
+    }
+    return value;
+  }
+
+  readOffset(offset) {
+    if (this._bigTiff) {
+      return this.readUint64(offset);
+    }
+    return this.readUint32(offset);
+  }
+}