Return Decoded struct with bytes read

.eslintrc.json

@@ -4,6 +4,7 @@
     "eslint:recommended",
     "plugin:@typescript-eslint/recommended"
   ],
+  "ignorePatterns": ["dist/"],
   "plugins": ["import", "jsdoc"],
   "rules": {
     "@typescript-eslint/no-explicit-any": "warn",

README.md

@@ -8,3 +8,11 @@
 JavaScript parser for [Apache Parquet](https://parquet.apache.org) files.
 
 Apache Parquet is an open source, column-oriented data file format designed for efficient data storage and retrieval.
+
+## References
+
+ - https://github.com/apache/parquet-format
+ - https://github.com/dask/fastparquet
+ - https://github.com/apache/thrift
+ - https://github.com/google/snappy
+ - https://github.com/zhipeng-jia/snappyjs

src/thrift.ts

@@ -1,3 +1,12 @@
+/**
+ * Represents a decoded value, and includes the number of bytes read.
+ * This is used to read data from the file and advance a virtual file pointer.
+ */
+interface Decoded<T> {
+  value: T
+  byteLength: number
+}
+
 // TCompactProtocol types
 const CompactType = {
   STOP: 0,
@@ -19,16 +28,16 @@ const CompactType = {
 /**
  * Parse TCompactProtocol
  */
-export function deserializeTCompactProtocol(buffer: ArrayBuffer): [number, Record<string, any>] {
+export function deserializeTCompactProtocol(buffer: ArrayBuffer): Decoded<Record<string, any>> {
   const view = new DataView(buffer)
-  let index = 0
+  let byteLength = 0
   let lastFid = 0
-  const result: Record<string, any> = {}
+  const value: Record<string, any> = {}
 
-  while (index < buffer.byteLength) {
+  while (byteLength < buffer.byteLength) {
     // Parse each field based on its type and add to the result object
-    const [type, fid, newIndex, newLastFid] = readFieldBegin(view, index, lastFid)
-    index = newIndex
+    const [type, fid, newIndex, newLastFid] = readFieldBegin(view, byteLength, lastFid)
+    byteLength = newIndex
     lastFid = newLastFid
 
     if (type === CompactType.STOP) {
@@ -37,11 +46,11 @@ export function deserializeTCompactProtocol(buffer: ArrayBuffer): [number, Recor
 
     // Handle the field based on its type
     let fieldValue
-    [fieldValue, index] = readElement(view, type, index)
-    result[`field_${fid}`] = fieldValue
+    [fieldValue, byteLength] = readElement(view, type, byteLength)
+    value[`field_${fid}`] = fieldValue
   }
 
-  return [ index, result ]
+  return { value, byteLength }
 }
 
 /**

test/thrift.test.ts

@@ -63,18 +63,18 @@ describe('deserializeTCompactProtocol function', () => {
     // Mark the end of the structure
     view.setUint8(index, 0x00) // STOP field
 
-    const [bufferLength, result] = deserializeTCompactProtocol(buffer)
-    expect(bufferLength).toBe(index + 1)
+    const { byteLength, value } = deserializeTCompactProtocol(buffer)
+    expect(byteLength).toBe(index + 1)
 
     // Assertions for each basic type
-    expect(result.field_1).toBe(true) // TRUE
-    expect(result.field_2).toBe(false) // FALSE
-    expect(result.field_3).toBe(0x7f) // BYTE
-    expect(result.field_4).toBe(0x7fff) // I16
-    expect(result.field_5).toBe(0x7fffffff) // I32
-    expect(result.field_6).toBe(BigInt('0x7fffffffffffffff')) // I64
-    expect(result.field_7).toBeCloseTo(123.456) // DOUBLE
-    expect(result.field_8).toBe('Hello, Thrift!') // STRING
+    expect(value.field_1).toBe(true) // TRUE
+    expect(value.field_2).toBe(false) // FALSE
+    expect(value.field_3).toBe(0x7f) // BYTE
+    expect(value.field_4).toBe(0x7fff) // I16
+    expect(value.field_5).toBe(0x7fffffff) // I32
+    expect(value.field_6).toBe(BigInt('0x7fffffffffffffff')) // I64
+    expect(value.field_7).toBeCloseTo(123.456) // DOUBLE
+    expect(value.field_8).toBe('Hello, Thrift!') // STRING
   })
 
 })