From 58cb0f7216941823cffbcc50f3a6adf30af88a70 Mon Sep 17 00:00:00 2001
From: Martin Hans <martin@artnim.io>
Date: Fri, 23 Aug 2024 18:32:34 +0200
Subject: [PATCH] Always return the count of actually copied items.

Further, reduce duplicated code by introduce `Decode<T>(...) where T :
struct`.
---
 src/Parquet/Encodings/ParquetPlainEncoder.cs | 36 +++-----------------
 1 file changed, 4 insertions(+), 32 deletions(-)

diff --git a/src/Parquet/Encodings/ParquetPlainEncoder.cs b/src/Parquet/Encodings/ParquetPlainEncoder.cs
index 953e5f62..85fef7f5 100644
--- a/src/Parquet/Encodings/ParquetPlainEncoder.cs
+++ b/src/Parquet/Encodings/ParquetPlainEncoder.cs
@@ -1,8 +1,10 @@
 using System;
 using System.Buffers;
+using System.Drawing;
 using System.IO;
 using System.Linq;
 using System.Numerics;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using Parquet.Data;
 using Parquet.Extensions;
@@ -593,54 +595,30 @@ public static void Encode(ReadOnlySpan<int> data, Stream destination) {
             Write(destination, bytes);
         }
 
-        public static int Decode(Span<byte> source, Span<int> data) {
-            Span<byte> dataBytes = MemoryMarshal.AsBytes(data);
-            source.CopyWithLimitTo(dataBytes);
-            return data.Length;
-        }
-
         public static void Encode(ReadOnlySpan<uint> data, Stream destination) {
             ReadOnlySpan<byte> bytes = MemoryMarshal.AsBytes(data);
             Write(destination, bytes);
         }
 
-        public static int Decode(Span<byte> source, Span<uint> data) {
-            Span<byte> bytes = MemoryMarshal.AsBytes(data);
-            source.CopyWithLimitTo(bytes);
-            return data.Length;
-        }
-
         public static void Encode(ReadOnlySpan<long> data, Stream destination) {
             ReadOnlySpan<byte> bytes = MemoryMarshal.AsBytes(data);
             Write(destination, bytes);
         }
 
-        public static int Decode(Span<byte> source, Span<long> data) {
-            Span<byte> bytes = MemoryMarshal.AsBytes(data);
-            source.CopyWithLimitTo(bytes);
-            return data.Length;
-        }
-
         public static void Encode(ReadOnlySpan<ulong> data, Stream destination) {
             ReadOnlySpan<byte> bytes = MemoryMarshal.AsBytes(data);
             Write(destination, bytes);
         }
 
-        public static int Decode(Span<byte> source, Span<ulong> data) {
-            Span<byte> bytes = MemoryMarshal.AsBytes(data);
-            source.CopyWithLimitTo(bytes);
-            return data.Length;
-        }
-
         public static void Encode(ReadOnlySpan<BigInteger> data, Stream destination) {
             ReadOnlySpan<byte> bytes = MemoryMarshal.AsBytes(data);
             Write(destination, bytes);
         }
 
-        public static int Decode(Span<byte> source, Span<BigInteger> data) {
+        public static int Decode<T>(Span<byte> source, Span<T> data) where T : struct {
             Span<byte> bytes = MemoryMarshal.AsBytes(data);
             source.CopyWithLimitTo(bytes);
-            return data.Length;
+            return Math.Min(data.Length, source.Length / Unsafe.SizeOf<T>());
         }
 
         public static void Encode(ReadOnlySpan<decimal> data, Stream destination, SchemaElement tse) {
@@ -752,12 +730,6 @@ public static void Encode(ReadOnlySpan<double> data, Stream destination) {
             Write(destination, bytes);
         }
 
-        public static int Decode(Span<byte> source, Span<double> data) {
-            Span<byte> bytes = MemoryMarshal.AsBytes(data);
-            source.CopyWithLimitTo(bytes);
-            return data.Length;
-        }
-
         public static void Encode(ReadOnlySpan<float> data, Stream destination) {
             ReadOnlySpan<byte> bytes = MemoryMarshal.AsBytes(data);
             Write(destination, bytes);