ntcore: Initial commit.

Change-Id: Id8df275a34aaa628581b18e39014b880c29bf9b2

src/nt_leb128.cpp

@@ -0,0 +1,133 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2015. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "nt_leb128.h"
+
+#include "nt_raw_istream.h"
+
+namespace NtImpl {
+
+/**
+ * size_uleb128 - get size of unsigned LEB128 data
+ * @val: value
+ *
+ * Determine the number of bytes required to encode an unsigned LEB128 datum.
+ * The algorithm is taken from Appendix C of the DWARF 3 spec. For information
+ * on the encodings refer to section "7.6 - Variable Length Data". Return
+ * the number of bytes required.
+ */
+std::size_t
+size_uleb128(unsigned long val)
+{
+    std::size_t count = 0;
+    do {
+        val >>= 7;
+        ++count;
+    } while (val != 0);
+    return count;
+}
+
+/**
+ * write_uleb128 - write unsigned LEB128 data
+ * @addr: the address where the ULEB128 data is to be stored
+ * @val: value to be stored
+ *
+ * Encode an unsigned LEB128 encoded datum. The algorithm is taken
+ * from Appendix C of the DWARF 3 spec. For information on the
+ * encodings refer to section "7.6 - Variable Length Data". Return
+ * the number of bytes written.
+ */
+std::size_t
+write_uleb128(char *addr, unsigned long val)
+{
+    std::size_t count = 0;
+
+    do {
+        unsigned char byte = val & 0x7f;
+        val >>= 7;
+
+        if (val != 0)
+            byte |= 0x80; // mark this byte to show that more bytes will follow
+
+        *((unsigned char *)addr) = byte;
+        addr++;
+        count++;
+    } while (val != 0);
+
+    return count;
+}
+
+/**
+ * read_uleb128 - read unsigned LEB128 data
+ * @addr: the address where the ULEB128 data is stored
+ * @ret: address to store the result
+ *
+ * Decode an unsigned LEB128 encoded datum. The algorithm is taken
+ * from Appendix C of the DWARF 3 spec. For information on the
+ * encodings refer to section "7.6 - Variable Length Data". Return
+ * the number of bytes read.
+ */
+std::size_t
+read_uleb128(char *addr, unsigned long *ret)
+{
+    unsigned long result = 0;
+    int shift = 0;
+    std::size_t count = 0;
+
+    while (1)
+    {
+        unsigned char byte = *((unsigned char *)addr);
+        addr++;
+        count++;
+
+        result |= (byte & 0x7f) << shift;
+        shift += 7;
+
+        if (!(byte & 0x80))
+             break;
+    }
+
+    *ret = result;
+
+    return count;
+}
+
+/**
+ * read_uleb128 - read unsigned LEB128 data from a stream
+ * @is: the input stream where the ULEB128 data is to be read from
+ * @ret: address to store the result
+ *
+ * Decode an unsigned LEB128 encoded datum. The algorithm is taken
+ * from Appendix C of the DWARF 3 spec. For information on the
+ * encodings refer to section "7.6 - Variable Length Data". Return
+ * false on stream error, true on success.
+ */
+bool
+read_uleb128(raw_istream &is, unsigned long *ret)
+{
+    unsigned long result = 0;
+    int shift = 0;
+
+    while (1)
+    {
+        unsigned char byte;
+        if (!is.read((char*)&byte, 1))
+            return false;
+
+        result |= (byte & 0x7f) << shift;
+        shift += 7;
+
+        if (!(byte & 0x80))
+             break;
+    }
+
+    *ret = result;
+
+    return true;
+}
+
+} // namespace NtImpl