varint: make it available outside the context of pack

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Makefile b/Makefile
index be1957a5e986d2e0581123dfe4e0eeb6702c13dc..0f26c879d83d1707ea4aa51a1851efd01d7b4653 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -627,6 +627,7 @@ LIB_H += tree-walk.h
 LIB_H += unpack-trees.h
 LIB_H += userdiff.h
 LIB_H += utf8.h
+LIB_H += varint.h
 LIB_H += xdiff-interface.h
 LIB_H += xdiff/xdiff.h
 
@@ -752,6 +753,7 @@ LIB_OBJS += url.o
 LIB_OBJS += usage.o
 LIB_OBJS += userdiff.o
 LIB_OBJS += utf8.o
+LIB_OBJS += varint.o
 LIB_OBJS += walker.o
 LIB_OBJS += wrapper.o
 LIB_OBJS += write_or_die.o

diff --git a/varint.c b/varint.c
new file mode 100644 (file)
index 0000000..4ed7729
--- /dev/null
+++ b/varint.c
@@ -0,0 +1,29 @@
+#include "varint.h"
+
+uintmax_t decode_varint(const unsigned char **bufp)
+{
+       const unsigned char *buf = *bufp;
+       unsigned char c = *buf++;
+       uintmax_t val = c & 127;
+       while (c & 128) {
+               val += 1;
+               if (!val || MSB(val, 7))
+                       return 0; /* overflow */
+               c = *buf++;
+               val = (val << 7) + (c & 127);
+       }
+       *bufp = buf;
+       return val;
+}
+
+int encode_varint(uintmax_t value, unsigned char *buf)
+{
+       unsigned char varint[16];
+       unsigned pos = sizeof(varint) - 1;
+       varint[pos] = value & 127;
+       while (value >>= 7)
+               varint[--pos] = 128 | (--value & 127);
+       if (buf)
+               memcpy(buf, varint + pos, sizeof(varint) - pos);
+       return sizeof(varint) - pos;
+}

diff --git a/varint.h b/varint.h
new file mode 100644 (file)
index 0000000..0321195
--- /dev/null
+++ b/varint.h
@@ -0,0 +1,9 @@
+#ifndef VARINT_H
+#define VARINT_H
+
+#include "git-compat-util.h"
+
+extern int encode_varint(uintmax_t, unsigned char *);
+extern uintmax_t decode_varint(const unsigned char **);
+
+#endif /* VARINT_H */