From 7f63a92679f524fb79c62134662a6713d3a61b3d Mon Sep 17 00:00:00 2001
From: Kenny Daniel <platypii@gmail.com>
Date: Sun, 11 Feb 2024 21:35:07 -0800
Subject: [PATCH] Handle conversion of decimal byte array

---
 src/column.js | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/column.js b/src/column.js
index f263e93..3a270c2 100644
--- a/src/column.js
+++ b/src/column.js
@@ -186,8 +186,7 @@ function convert(data, schemaElement) {
     if (typeof data[0] === 'number') {
       return data.map(v => v * scaleFactor)
     } else {
-      // TODO: parse byte string
-      throw new Error('parquet decimal byte string not supported')
+      return data.map(v => parseDecimal(v) * scaleFactor)
     }
   }
   if (ctype === 'DATE') {
@@ -207,3 +206,18 @@ function convert(data, schemaElement) {
   }
   return data
 }
+
+/**
+ * Parse decimal from byte array.
+ *
+ * @param {Uint8Array} bytes
+ * @returns {number}
+ */
+function parseDecimal(bytes) {
+  // TODO: handle signed
+  let value = 0
+  for (const byte of bytes) {
+    value = value << 8 | byte
+  }
+  return value
+}