bitmanipulation: add utils to read/write bigendian 64bit integers

Differential Revision: https://phab.mercurial-scm.org/D9845

mercurial/bitmanipulation.h

@@ -5,6 +5,18 b''
 
 #include "compat.h"
 
+/* Reads a 64 bit integer from big-endian bytes. Assumes that the data is long
+ enough */
+static inline uint64_t getbe64(const char *c)
+{
+	const unsigned char *d = (const unsigned char *)c;
+
+	return ((((uint64_t)d[0]) << 56) | (((uint64_t)d[1]) << 48) |
+	        (((uint64_t)d[2]) << 40) | (((uint64_t)d[3]) << 32) |
+	        (((uint64_t)d[4]) << 24) | (((uint64_t)d[5]) << 16) |
+	        (((uint64_t)d[6]) << 8) | (d[7]));
+}
+
 static inline uint32_t getbe32(const char *c)
 {
 	const unsigned char *d = (const unsigned char *)c;
@@ -27,6 +39,20 b' static inline uint16_t getbeuint16(const'
 	return ((d[0] << 8) | (d[1]));
 }
 
+/* Writes a 64 bit integer to bytes in a big-endian format.
+ Assumes that the buffer is long enough */
+static inline void putbe64(uint64_t x, char *c)
+{
+	c[0] = (x >> 56) & 0xff;
+	c[1] = (x >> 48) & 0xff;
+	c[2] = (x >> 40) & 0xff;
+	c[3] = (x >> 32) & 0xff;
+	c[4] = (x >> 24) & 0xff;
+	c[5] = (x >> 16) & 0xff;
+	c[6] = (x >> 8) & 0xff;
+	c[7] = (x)&0xff;
+}
+
 static inline void putbe32(uint32_t x, char *c)
 {
 	c[0] = (x >> 24) & 0xff;