Patchwork [16/22] Add uleb encoding/decoding functions

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Submitter Juan Quintela
Date July 13, 2012, 7:23 a.m.
Message ID <1342164224-32709-17-git-send-email-quintela@redhat.com>
Download mbox | patch
Permalink /patch/170812/
State New
Headers show

Comments

Juan Quintela - July 13, 2012, 7:23 a.m.
From: Orit Wasserman <owasserm@redhat.com>

Implement Unsigned Little Endian Base 128.

Signed-off-by: Orit Wasserman <owasserm@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 cutils.c      |   33 +++++++++++++++++++++++++++++++++
 qemu-common.h |    8 ++++++++
 2 files changed, 41 insertions(+)

Patch

diff --git a/cutils.c b/cutils.c
index b0bdd4b..700f943 100644
--- a/cutils.c
+++ b/cutils.c
@@ -384,3 +384,36 @@  int64_t pow2floor(int64_t value)
     }
     return value;
 }
+
+/*
+ * Implementation of  ULEB128 (http://en.wikipedia.org/wiki/LEB128)
+ * Input is limited to 14-bit numbers
+ */
+int uleb128_encode_small(uint8_t *out, uint32_t n)
+{
+    g_assert(n <= 0x3fff);
+    if (n < 0x80) {
+        *out++ = n;
+        return 1;
+    } else {
+        *out++ = (n & 0x7f) | 0x80;
+        *out++ = n >> 7;
+        return 2;
+    }
+}
+
+int uleb128_decode_small(const uint8_t *in, uint32_t *n)
+{
+    if (!(*in & 0x80)) {
+        *n = *in++;
+        return 1;
+    } else {
+        *n = *in++ & 0x7f;
+        /* we exceed 14 bit number */
+        if (*in & 0x80) {
+            return -1;
+        }
+        *n |= *in++ << 7;
+        return 2;
+    }
+}
diff --git a/qemu-common.h b/qemu-common.h
index 195bab5..3188bdd 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -426,4 +426,12 @@  int64_t pow2floor(int64_t value);

 #include "module.h"

+/*
+ * Implementation of ULEB128 (http://en.wikipedia.org/wiki/LEB128)
+ * Input is limited to 14-bit numbers
+ */
+
+int uleb128_encode_small(uint8_t *out, uint32_t n);
+int uleb128_decode_small(const uint8_t *in, uint32_t *n);
+
 #endif