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include/utils/palloc.h

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+/*-------------------------------------------------------------------------
+ *
+ * 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) 1996-2012, 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;
+
+/*
+ * CurrentMemoryContext is the default allocation context for palloc().
+ * We declare it here so that palloc() can be a macro.	Avoid accessing it
+ * directly!  Instead, use MemoryContextSwitchTo() to change the setting.
+ */
+extern PGDLLIMPORT __thread MemoryContext CurrentMemoryContext;
+
+/*
+ * 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);
+
+#define palloc(sz) MemoryContextAlloc(CurrentMemoryContext, (sz))
+
+#define palloc0(sz) MemoryContextAllocZero(CurrentMemoryContext, (sz))
+
+/*
+ * 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))
+
+extern void pfree(void *pointer);
+
+extern void *repalloc(void *pointer, Size size);
+
+/*
+ * MemoryContextSwitchTo can't be a macro in standard C compilers.
+ * But we can make it an inline function if the compiler supports it.
+ *
+ * This file has to be includable by some non-backend code such as
+ * pg_resetxlog, so don't expose the CurrentMemoryContext reference
+ * if FRONTEND is defined.
+ */
+#if defined(USE_INLINE) && !defined(FRONTEND)
+
+static inline MemoryContext
+MemoryContextSwitchTo(MemoryContext context) {
+    MemoryContext old = CurrentMemoryContext;
+
+    CurrentMemoryContext = context;
+    return old;
+}
+
+#else
+
+extern MemoryContext MemoryContextSwitchTo(MemoryContext context);
+#endif /* USE_INLINE && !FRONTEND */
+
+/*
+ * 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);
+
+#define pstrdup(str) MemoryContextStrdup(CurrentMemoryContext, (str))
+
+extern char *pnstrdup(const char *in, Size len);
+
+#if defined(WIN32) || defined(__CYGWIN__)
+extern void *pgport_palloc(Size sz);
+extern char *pgport_pstrdup(const char *str);
+extern void pgport_pfree(void *pointer);
+#endif
+
+#endif /* PALLOC_H */