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/* Licensed under LGPLv2.1+ - see LICENSE file for details */
#ifndef CCAN_CAST_H
#define CCAN_CAST_H
#include "config.h"
#include <stdint.h>
#include <ccan/build_assert/build_assert.h>
/**
* cast_signed - cast a (const) char * to/from (const) signed/unsigned char *.
* @type: some char * variant.
* @expr: expression (of some char * variant) to cast.
*
* Some libraries insist on an unsigned char in various places; cast_signed
* makes sure (with suitable compiler) that the expression you are casting
* only differs in signed/unsigned, not in type or const-ness.
*/
#define cast_signed(type, expr) \
((type)(expr) \
+ BUILD_ASSERT_OR_ZERO(cast_sign_compatible(type, (expr))))
/**
* cast_const - remove a const qualifier from a pointer.
* @type: some pointer type.
* @expr: expression to cast.
*
* This ensures that you are only removing the const qualifier from an
* expression. The expression must otherwise match @type.
*
* If @type is a pointer to a pointer, you must use cast_const2 (etc).
*
* Example:
* // Dumb open-coded strstr variant.
* static char *find_needle(const char *haystack)
* {
* size_t i;
* for (i = 0; i < strlen(haystack); i++)
* if (memcmp("needle", haystack+i, strlen("needle")) == 0)
* return cast_const(char *, haystack+i);
* return NULL;
* }
*/
#define cast_const(type, expr) \
((type)((intptr_t)(expr) \
+ BUILD_ASSERT_OR_ZERO(cast_const_compat1((expr), type))))
/**
* cast_const2 - remove a const qualifier from a pointer to a pointer.
* @type: some pointer to pointer type.
* @expr: expression to cast.
*
* This ensures that you are only removing the const qualifier from an
* expression. The expression must otherwise match @type.
*/
#define cast_const2(type, expr) \
((type)((intptr_t)(expr) \
+ BUILD_ASSERT_OR_ZERO(cast_const_compat2((expr), type))))
/**
* cast_const3 - remove a const from a pointer to a pointer to a pointer..
* @type: some pointer to pointer to pointer type.
* @expr: expression to cast.
*
* This ensures that you are only removing the const qualifier from an
* expression. The expression must otherwise match @type.
*/
#define cast_const3(type, expr) \
((type)((intptr_t)(expr) \
+ BUILD_ASSERT_OR_ZERO(cast_const_compat3((expr), type))))
/**
* cast_static - explicit mimic of implicit cast.
* @type: some type.
* @expr: expression to cast.
*
* This ensures that the cast is not to or from a pointer: it can only be
* an implicit cast, such as a pointer to a similar const pointer, or between
* integral types.
*/
#if HAVE_COMPOUND_LITERALS
#define cast_static(type, expr) \
((struct { type x; }){(expr)}.x)
#else
#define cast_static(type, expr) \
((type)(expr))
#endif
/* Herein lies the gcc magic to evoke compile errors. */
#if HAVE_BUILTIN_CHOOSE_EXPR && HAVE_BUILTIN_TYPES_COMPATIBLE_P && HAVE_TYPEOF
#define cast_sign_compatible(t, e) \
__builtin_choose_expr( \
__builtin_types_compatible_p(__typeof__(t), char *) || \
__builtin_types_compatible_p(__typeof__(t), signed char *) || \
__builtin_types_compatible_p(__typeof__(t), unsigned char *), \
/* if type is not const qualified */ \
__builtin_types_compatible_p(__typeof__(e), char *) || \
__builtin_types_compatible_p(__typeof__(e), signed char *) || \
__builtin_types_compatible_p(__typeof__(e), unsigned char *), \
/* and if it is... */ \
__builtin_types_compatible_p(__typeof__(e), const char *) || \
__builtin_types_compatible_p(__typeof__(e), const signed char *) || \
__builtin_types_compatible_p(__typeof__(e), const unsigned char *) ||\
__builtin_types_compatible_p(__typeof__(e), char *) || \
__builtin_types_compatible_p(__typeof__(e), signed char *) || \
__builtin_types_compatible_p(__typeof__(e), unsigned char *) \
)
#define cast_const_strip1(expr) \
__typeof__(*(struct { int z; __typeof__(expr) x; }){0}.x)
#define cast_const_strip2(expr) \
__typeof__(**(struct { int z; __typeof__(expr) x; }){0}.x)
#define cast_const_strip3(expr) \
__typeof__(***(struct { int z; __typeof__(expr) x; }){0}.x)
#define cast_const_compat1(expr, type) \
__builtin_types_compatible_p(cast_const_strip1(expr), \
cast_const_strip1(type))
#define cast_const_compat2(expr, type) \
__builtin_types_compatible_p(cast_const_strip2(expr), \
cast_const_strip2(type))
#define cast_const_compat3(expr, type) \
__builtin_types_compatible_p(cast_const_strip3(expr), \
cast_const_strip3(type))
#else
#define cast_sign_compatible(type, expr) \
(sizeof(*(type)0) == 1 && sizeof(*(expr)) == 1)
#define cast_const_compat1(expr, type) (1)
#define cast_const_compat2(expr, type) (1)
#define cast_const_compat3(expr, type) (1)
#endif
#endif /* CCAN_CAST_H */
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