From 40fd9d8cf79168200728c88944d80bdda9cb533d Mon Sep 17 00:00:00 2001
From: TermiNexus <wyt18222152539wyt@163.com>
Date: Tue, 13 Oct 2026 16:34:37 +0800
Subject: [PATCH] =?UTF-8?q?fix(base64):=20=E5=9B=A0=E5=8F=96=E6=B6=88?=
 =?UTF-8?q?=E6=95=B4=E6=95=B0=E6=8F=90=E5=8D=87=EF=BC=8Cb64decode=20?=
 =?UTF-8?q?=E7=A7=BB=E4=BD=8D=E5=B7=A6=E6=93=8D=E4=BD=9C=E6=95=B0=E6=98=BE?=
 =?UTF-8?q?=E5=BC=8F=E5=8A=A0=E5=AE=BD=E4=B8=BA=20uint32=EF=BC=88=E4=BF=AE?=
 =?UTF-8?q?=E7=A7=BB=E4=BD=8D=E8=AE=A1=E6=95=B0=E8=B6=8A=E7=95=8C=E4=B8=8E?=
 =?UTF-8?q?=E9=9D=99=E9=BB=98=E6=88=AA=E6=96=AD=EF=BC=89?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 base64.vp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/base64.vp b/base64.vp
index eb39e33..3123266 100644
--- a/base64.vp
+++ b/base64.vp
@@ -56,11 +56,13 @@ def b64decode(s: str, out: uint8*) -> sizet:
         val = 0
         # Parse 6-bit values sequentially
         c = s[i] - 43
-        val |= (b64_dec_tab[c] & 0x3F) << 18
+        # 整数提升取消后，`& 0x3F` 的无损常量适配会把左操作数留成 i8（位宽仅 8），<< 18 / << 12 越界报错；
+        # 显式 uint32() 把左操作数加宽到 32 位后再移位（与上方编码段 uint32(...) << 16 的先例一致）。
+        val |= uint32(b64_dec_tab[c] & 0x3F) << 18
         c = s[i+1] - 43
-        val |= (b64_dec_tab[c] & 0x3F) << 12
+        val |= uint32(b64_dec_tab[c] & 0x3F) << 12
         c = s[i+2] - 43
-        if s[i+2] != '=': val |= (b64_dec_tab[c] & 0x3F) << 6
+        if s[i+2] != '=': val |= uint32(b64_dec_tab[c] & 0x3F) << 6  # 同上：i8 左操作数左移 6 位会截断高位（静默回绕）
         c = s[i+3] - 43
         if s[i+3] != '=': val |= (b64_dec_tab[c] & 0x3F)
         # Write recovered bytes