upstream/mercurial-mirror Files · mercurial/bitmanipulation.h

rust-pyo3: simplified API to get core Index references...

rust-pyo3: simplified API to get core Index references Given the amount of conversion and arcane internal detail, it is easier for the caller and makes a better separation of concerns to just introduce a new unsafe helper. It is actually possible that it would be safe, and we can decide about that later. Actually the reason given in the `cpython` crate for unsafety of the `try_borrow()` method is the following: ``` // try_borrow() and try_borrow_mut() are unsafe because self.data may // have a function returning the inner &'static reference. // If T is &'static U, its lifetime can be easily coerced to &'a U, but // how could we do that for Whatever<'static> in general? ``` Given that we coerce the Index reference to the GIL lifetime and that it is unlikely that the inner data would contain a function returning the a `'static` reference, it is possible that it is actually even safe.

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      #ifndef HG_BITMANIPULATION_H

      #define HG_BITMANIPULATION_H

      #include <string.h>

      #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;

      	return ((((uint32_t)d[0]) << 24) | (((uint32_t)d[1]) << 16) |

      	        (((uint32_t)d[2]) << 8) | (d[3]));

      }

      static inline int16_t getbeint16(const char *c)

      {

      	const unsigned char *d = (const unsigned char *)c;

      	return ((d[0] << 8) | (d[1]));

      }

      static inline uint16_t getbeuint16(const char *c)

      {

      	const unsigned char *d = (const unsigned char *)c;

      	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;

      	c[1] = (x >> 16) & 0xff;

      	c[2] = (x >> 8) & 0xff;

      	c[3] = (x)&0xff;

      }

      static inline double getbefloat64(const char *c)

      {

      	const unsigned char *d = (const unsigned char *)c;

      	double ret;

      	int i;

      	uint64_t t = 0;

      	for (i = 0; i < 8; i++) {

      		t = (t << 8) + d[i];

      	}

      	memcpy(&ret, &t, sizeof(t));

      	return ret;

      }

      #endif

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				#ifndef HG_BITMANIPULATION_H
				#define HG_BITMANIPULATION_H

				#include <string.h>

				#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;

				return ((((uint32_t)d[0]) << 24) \| (((uint32_t)d[1]) << 16) \|
				(((uint32_t)d[2]) << 8) \| (d[3]));
				}

				static inline int16_t getbeint16(const char *c)
				{
				const unsigned char d = (const unsigned char )c;

				return ((d[0] << 8) \| (d[1]));
				}

				static inline uint16_t getbeuint16(const char *c)
				{
				const unsigned char d = (const unsigned char )c;

				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;
				c[1] = (x >> 16) & 0xff;
				c[2] = (x >> 8) & 0xff;
				c[3] = (x)&0xff;
				}

				static inline double getbefloat64(const char *c)
				{
				const unsigned char d = (const unsigned char )c;
				double ret;
				int i;
				uint64_t t = 0;
				for (i = 0; i < 8; i++) {
				t = (t << 8) + d[i];
				}
				memcpy(&ret, &t, sizeof(t));
				return ret;
				}

				#endif