First commit

1 files changed, 75 insertions, 0 deletions

diff --git a/src/io/leb128.c b/src/io/leb128.c
new file mode 100644
index 0000000..efb599b
--- /dev/null
+++ b/src/io/leb128.c
@@ -0,0 +1,75 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+
+/* The functions below is a (somewhat heavily) modified version of that
+ * provided by the wac project: https://github.com/kanaka/wac
+ *
+ * Copyright (C) Joel Martin <github@martintribe.org>
+ * The wac project is licensed under the MPL 2.0 (Mozilla Public License
+ * 2.0). The text of the MPL 2.0 license is included below and can be
+ * found at https://www.mozilla.org/MPL/2.0/
+ */
+
+#include <nanowasm/types.h>
+#include <nw/io.h>
+#include <nw/log.h>
+
+enum nw_state nwp_leb128(const struct nw_io_cfg *const cfg,
+    struct nw_sm_leb128 *const l, const unsigned maxbits, const int sign,
+    void *const user)
+{
+    unsigned char byte;
+
+    for (;;)
+    {
+        const int n = cfg->read(&byte, sizeof byte, user);
+        unsigned long v;
+
+        if (n < 0)
+            return NW_FATAL;
+        else if (!n)
+            return NW_AGAIN;
+
+        v = (unsigned long)(byte & 0x7f) << l->shift;;
+
+        if (l->shift < 32)
+            l->result.low |= v;
+        else
+            l->result.hi |= v;
+
+        l->shift += 7;
+
+        if (!(byte & 0x80))
+            break;
+        else if (++l->bcnt > (maxbits + 7u - 1u) / 7u)
+        {
+#ifdef NW_LOG
+            long offset;
+            const enum nw_state n = cfg->tell(&offset, cfg->user);
+
+            if (n)
+                return n;
+
+            nwp_log("leb128 overflow, offset=%#lx\n", (unsigned long)offset);
+#endif
+            return NW_FATAL;
+        }
+    }
+
+    if (sign && (l->shift < maxbits) && (byte & 0x40))
+    {
+        if (l->shift < 32)
+            l->result.low |= -1l << (l->shift);
+        else
+            l->result.hi |= -1l << (l->shift);
+    }
+
+    return NW_OK;
+}