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ensure: replace pow2gt with multiplication by two

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This replaces the bit fiddling involved with calculating a new buffer
size by just multiplying the required length by two, paving the way to a
complete switch to size_t at a later point in time.
This commit is contained in:
Max Bruckner 2017-02-16 00:11:34 +01:00
parent 123bb1af7b
commit 9f6fa94c91
1 changed files with 15 additions and 36 deletions
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51
cJSON.c
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@ -32,20 +32,6 @@
#include <ctype.h> #include <ctype.h>
#include "cJSON.h" #include "cJSON.h"
/* Determine the number of bits that an integer has using the preprocessor */
#if INT_MAX == 32767
/* 16 bits */
#define INTEGER_SIZE 0x0010
#elif INT_MAX == 2147483647
/* 32 bits */
#define INTEGER_SIZE 0x0100
#elif INT_MAX == 9223372036854775807
/* 64 bits */
#define INTEGER_SIZE 0x1000
#else
#error "Failed to determine the size of an integer"
#endif
/* define our own boolean type */ /* define our own boolean type */
typedef int cjbool; typedef int cjbool;
#define true ((cjbool)1) #define true ((cjbool)1)
@ -223,27 +209,6 @@ double cJSON_SetNumberHelper(cJSON *object, double number)
return object->valuedouble = number; return object->valuedouble = number;
} }
/* calculate the next largest power of 2 */
static int pow2gt (int x)
{
--x;
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
#if INTEGER_SIZE & 0x1110 /* at least 16 bit */
x |= x >> 8;
#endif
#if INTEGER_SIZE & 0x1100 /* at least 32 bit */
x |= x >> 16;
#endif
#if INTEGER_SIZE & 0x1000 /* 64 bit */
x |= x >> 32;
#endif
return x + 1;
}
typedef struct typedef struct
{ {
unsigned char *buffer; unsigned char *buffer;
@ -278,7 +243,21 @@ static unsigned char* ensure(printbuffer *p, size_t needed)
return NULL; return NULL;
} }
newsize = (size_t) pow2gt((int)needed); /* calculate new buffer size */
newsize = needed * 2;
if (newsize > INT_MAX)
{
/* overflow of int, use INT_MAX if possible */
if (needed <= INT_MAX)
{
newsize = INT_MAX;
}
else
{
return NULL;
}
}
newbuffer = (unsigned char*)cJSON_malloc(newsize); newbuffer = (unsigned char*)cJSON_malloc(newsize);
if (!newbuffer) if (!newbuffer)
{ {