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Diffstat (limited to 'src/include/utils/palloc.h')
| -rw-r--r-- | src/include/utils/palloc.h | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/src/include/utils/palloc.h b/src/include/utils/palloc.h new file mode 100644 index 0000000..399e5c8 --- /dev/null +++ b/src/include/utils/palloc.h @@ -0,0 +1,136 @@ +/*------------------------------------------------------------------------- + * + * palloc.h + * POSTGRES memory allocator definitions. + * + * This file contains the basic memory allocation interface that is + * needed by almost every backend module. It is included directly by + * postgres.h, so the definitions here are automatically available + * everywhere. Keep it lean! + * + * Memory allocation occurs within "contexts". Every chunk obtained from + * palloc()/MemoryContextAlloc() is allocated within a specific context. + * The entire contents of a context can be freed easily and quickly by + * resetting or deleting the context --- this is both faster and less + * prone to memory-leakage bugs than releasing chunks individually. + * We organize contexts into context trees to allow fine-grain control + * over chunk lifetime while preserving the certainty that we will free + * everything that should be freed. See utils/mmgr/README for more info. + * + * + * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * src/include/utils/palloc.h + * + *------------------------------------------------------------------------- + */ +#ifndef PALLOC_H +#define PALLOC_H + +/* + * Type MemoryContextData is declared in nodes/memnodes.h. Most users + * of memory allocation should just treat it as an abstract type, so we + * do not provide the struct contents here. + */ +typedef struct MemoryContextData *MemoryContext; + +/* + * A memory context can have callback functions registered on it. Any such + * function will be called once just before the context is next reset or + * deleted. The MemoryContextCallback struct describing such a callback + * typically would be allocated within the context itself, thereby avoiding + * any need to manage it explicitly (the reset/delete action will free it). + */ +typedef void (*MemoryContextCallbackFunction) (void *arg); + +typedef struct MemoryContextCallback +{ + MemoryContextCallbackFunction func; /* function to call */ + void *arg; /* argument to pass it */ + struct MemoryContextCallback *next; /* next in list of callbacks */ +} MemoryContextCallback; + +/* + * CurrentMemoryContext is the default allocation context for palloc(). + * Avoid accessing it directly! Instead, use MemoryContextSwitchTo() + * to change the setting. + */ +extern PGDLLIMPORT MemoryContext CurrentMemoryContext; + +/* + * Flags for MemoryContextAllocExtended. + */ +#define MCXT_ALLOC_HUGE 0x01 /* allow huge allocation (> 1 GB) */ +#define MCXT_ALLOC_NO_OOM 0x02 /* no failure if out-of-memory */ +#define MCXT_ALLOC_ZERO 0x04 /* zero allocated memory */ + +/* + * Fundamental memory-allocation operations (more are in utils/memutils.h) + */ +extern void *MemoryContextAlloc(MemoryContext context, Size size); +extern void *MemoryContextAllocZero(MemoryContext context, Size size); +extern void *MemoryContextAllocZeroAligned(MemoryContext context, Size size); +extern void *MemoryContextAllocExtended(MemoryContext context, + Size size, int flags); + +extern void *palloc(Size size); +extern void *palloc0(Size size); +extern void *palloc_extended(Size size, int flags); +extern pg_nodiscard void *repalloc(void *pointer, Size size); +extern void pfree(void *pointer); + +/* + * The result of palloc() is always word-aligned, so we can skip testing + * alignment of the pointer when deciding which MemSet variant to use. + * Note that this variant does not offer any advantage, and should not be + * used, unless its "sz" argument is a compile-time constant; therefore, the + * issue that it evaluates the argument multiple times isn't a problem in + * practice. + */ +#define palloc0fast(sz) \ + ( MemSetTest(0, sz) ? \ + MemoryContextAllocZeroAligned(CurrentMemoryContext, sz) : \ + MemoryContextAllocZero(CurrentMemoryContext, sz) ) + +/* Higher-limit allocators. */ +extern void *MemoryContextAllocHuge(MemoryContext context, Size size); +extern pg_nodiscard void *repalloc_huge(void *pointer, Size size); + +/* + * Although this header file is nominally backend-only, certain frontend + * programs like pg_controldata include it via postgres.h. For some compilers + * it's necessary to hide the inline definition of MemoryContextSwitchTo in + * this scenario; hence the #ifndef FRONTEND. + */ + +#ifndef FRONTEND +static inline MemoryContext +MemoryContextSwitchTo(MemoryContext context) +{ + MemoryContext old = CurrentMemoryContext; + + CurrentMemoryContext = context; + return old; +} +#endif /* FRONTEND */ + +/* Registration of memory context reset/delete callbacks */ +extern void MemoryContextRegisterResetCallback(MemoryContext context, + MemoryContextCallback *cb); + +/* + * These are like standard strdup() except the copied string is + * allocated in a context, not with malloc(). + */ +extern char *MemoryContextStrdup(MemoryContext context, const char *string); +extern char *pstrdup(const char *in); +extern char *pnstrdup(const char *in, Size len); + +extern char *pchomp(const char *in); + +/* sprintf into a palloc'd buffer --- these are in psprintf.c */ +extern char *psprintf(const char *fmt,...) pg_attribute_printf(1, 2); +extern size_t pvsnprintf(char *buf, size_t len, const char *fmt, va_list args) pg_attribute_printf(3, 0); + +#endif /* PALLOC_H */ |