1 files changed, 77 insertions, 0 deletions
diff --git a/na/lib/decompress_lz4.cc b/na/lib/decompress_lz4.cc
new file mode 100644
index 0000000..6a93936
--- /dev/null
+++ b/na/lib/decompress_lz4.cc
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#include <lume/decompress.h>
+
+int lz4_decompress(const uint8* src, uint32 src_len, uint8* dst, uint32 dst_cap)
+{
+    const uint8* ip = src;
+    const uint8* iend = src + src_len;
+    uint8* op = dst;
+    uint8* oend = dst + dst_cap;
+
+    while (ip < iend) {
+        uint8 token = *ip++;
+        uint32 lit_len = token >> 4;
+
+        if (lit_len == 15) {
+            uint8 s = 0;
+            do {
+                if (ip >= iend) {
+                    return -1;
+                }
+                s = *ip++;
+                lit_len += s;
+            } while (s == 255);
+        }
+
+        if (ip + lit_len > iend) {
+            return -1;
+        }
+        if (op + lit_len > oend) {
+            return -1;
+        }
+
+        for (uint32 i = 0; i < lit_len; ++i) {
+            *op++ = *ip++;
+        }
+
+        if (ip >= iend) {
+            break;
+        }
+        if (ip + 2 > iend) {
+            return -1;
+        }
+
+        uint32 off = static_cast<uint32>(ip[0]) | (static_cast<uint32>(ip[1]) << 8);
+        ip += 2;
+        if (off == 0 || off > static_cast<uint32>(op - dst)) {
+            return -1;
+        }
+
+        uint32 match_len = token & 0x0F;
+        if (match_len == 15) {
+            uint8 s = 0;
+            do {
+                if (ip >= iend) {
+                    return -1;
+                }
+                s = *ip++;
+                match_len += s;
+            } while (s == 255);
+        }
+        match_len += 4;
+
+        if (op + match_len > oend) {
+            return -1;
+        }
+
+        uint8* match = op - off;
+        for (uint32 i = 0; i < match_len; ++i) {
+            op[i] = match[i];
+        }
+        op += match_len;
+    }
+
+    return static_cast<int>(op - dst);
+}