[refactoring] Extract read leb to a separate file, share the code between loader and mini loader (#3701)

There's probably a number of other places where the bh_leb_read could be used (e.g. aot loader)
but I'm making the change as small as possible. Further refactoring can be done later.

core/shared/utils/bh_leb128.c

@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include "bh_leb128.h"
+
+bh_leb_read_status_t
+bh_leb_read(const uint8 *buf, const uint8 *buf_end, uint32 maxbits, bool sign,
+            uint64 *p_result, size_t *p_offset)
+{
+    uint64 result = 0;
+    uint32 shift = 0;
+    uint32 offset = 0, bcnt = 0;
+    uint64 byte;
+
+    while (true) {
+        /* uN or SN must not exceed ceil(N/7) bytes */
+        if (bcnt + 1 > (maxbits + 6) / 7) {
+            return BH_LEB_READ_TOO_LONG;
+        }
+
+        if ((uintptr_t)buf + offset + 1 < (uintptr_t)buf
+            || (uintptr_t)buf + offset + 1 > (uintptr_t)buf_end) {
+            return BH_LEB_READ_UNEXPECTED_END;
+        }
+        byte = buf[offset];
+        offset += 1;
+        result |= ((byte & 0x7f) << shift);
+        shift += 7;
+        bcnt += 1;
+        if ((byte & 0x80) == 0) {
+            break;
+        }
+    }
+
+    if (!sign && maxbits == 32 && shift >= maxbits) {
+        /* The top bits set represent values > 32 bits */
+        if (((uint8)byte) & 0xf0)
+            return BH_LEB_READ_OVERFLOW;
+    }
+    else if (sign && maxbits == 32) {
+        if (shift < maxbits) {
+            /* Sign extend, second-highest bit is the sign bit */
+            if ((uint8)byte & 0x40)
+                result |= (~((uint64)0)) << shift;
+        }
+        else {
+            /* The top bits should be a sign-extension of the sign bit */
+            bool sign_bit_set = ((uint8)byte) & 0x8;
+            int top_bits = ((uint8)byte) & 0xf0;
+            if ((sign_bit_set && top_bits != 0x70)
+                || (!sign_bit_set && top_bits != 0))
+                return BH_LEB_READ_OVERFLOW;
+        }
+    }
+    else if (sign && maxbits == 64) {
+        if (shift < maxbits) {
+            /* Sign extend, second-highest bit is the sign bit */
+            if ((uint8)byte & 0x40)
+                result |= (~((uint64)0)) << shift;
+        }
+        else {
+            /* The top bits should be a sign-extension of the sign bit */
+            bool sign_bit_set = ((uint8)byte) & 0x1;
+            int top_bits = ((uint8)byte) & 0xfe;
+
+            if ((sign_bit_set && top_bits != 0x7e)
+                || (!sign_bit_set && top_bits != 0))
+                return BH_LEB_READ_OVERFLOW;
+        }
+    }
+
+    *p_offset = offset;
+    *p_result = result;
+    return BH_LEB_READ_SUCCESS;
+}

core/shared/utils/bh_leb128.h

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2024 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#ifndef _BH_LEB128_H
+#define _BH_LEB128_H
+
+#include "bh_platform.h"
+
+typedef enum {
+    BH_LEB_READ_SUCCESS,
+    BH_LEB_READ_TOO_LONG,
+    BH_LEB_READ_OVERFLOW,
+    BH_LEB_READ_UNEXPECTED_END,
+} bh_leb_read_status_t;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+bh_leb_read_status_t
+bh_leb_read(const uint8 *buf, const uint8 *buf_end, uint32 maxbits, bool sign,
+            uint64 *p_result, size_t *p_offset);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif