sqlite源码剖析(2)

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　　声明：本SQLite源码剖析系列为刘兴(http://deepfuture.iyunv.com/)原创，未经笔者授权，任何人和机构不能转载
　　/*
　　** The maximum number of opcodes in a VDBE program.
　　** Not currently enforced.
　　*/
　　//VDBE程序的最大操作码数目
　　#ifndef SQLITE_MAX_VDBE_OP
　　# define SQLITE_MAX_VDBE_OP 25000
　　#endif
　　 
　　/*
　　** The maximum number of arguments to an SQL function.
　　*/
　　//SQL函数的最大参数数目
　　#ifndef SQLITE_MAX_FUNCTION_ARG
　　# define SQLITE_MAX_FUNCTION_ARG 127
　　#endif
　　 
　　/*
　　** The maximum number of in-memory pages to use for the main database
　　** table and for temporary tables.  The SQLITE_DEFAULT_CACHE_SIZE
　　*/
　　//主数据库表和临时表的最大内存大小
　　#ifndef SQLITE_DEFAULT_CACHE_SIZE
　　# define SQLITE_DEFAULT_CACHE_SIZE  2000
　　#endif
　　#ifndef SQLITE_DEFAULT_TEMP_CACHE_SIZE
　　# define SQLITE_DEFAULT_TEMP_CACHE_SIZE  500
　　#endif
　　 
　　/*
　　** The maximum number of attached databases.  This must be between 0
　　** and 30.  The upper bound on 30 is because a 32-bit integer bitmap
　　** is used internally to track attached databases.
　　*/
　　//附加数据库的数目
　　#ifndef SQLITE_MAX_ATTACHED
　　# define SQLITE_MAX_ATTACHED 10
　　#endif
　　 
　　 
　　/*
　　** The maximum value of a ?nnn wildcard that the parser will accept.
　　*/
　　//解析器接受的匹配符参数最大值
　　#ifndef SQLITE_MAX_VARIABLE_NUMBER
　　# define SQLITE_MAX_VARIABLE_NUMBER 999
　　#endif
　　 
　　/* Maximum page size.  The upper bound on this value is 32768.  This a limit
　　** imposed by the necessity of storing the value in a 2-byte unsigned integer
　　** and the fact that the page size must be a power of 2.
　　**
　　** If this limit is changed, then the compiled library is technically
　　** incompatible with an SQLite library compiled with a different limit. If
　　** a process operating on a database with a page-size of 65536 bytes
　　** crashes, then an instance of SQLite compiled with the default page-size
　　** limit will not be able to rollback the aborted transaction. This could
　　** lead to database corruption.
　　*/
　　//最大页面大小
　　#ifndef SQLITE_MAX_PAGE_SIZE
　　# define SQLITE_MAX_PAGE_SIZE 32768
　　#endif
　　 
　　 
　　/*
　　** The default size of a database page.
　　*/
　　//数据库页面的默认大小
　　#ifndef SQLITE_DEFAULT_PAGE_SIZE
　　# define SQLITE_DEFAULT_PAGE_SIZE 1024
　　#endif
　　#if SQLITE_DEFAULT_PAGE_SIZE>SQLITE_MAX_PAGE_SIZE
　　# undef SQLITE_DEFAULT_PAGE_SIZE
　　# define SQLITE_DEFAULT_PAGE_SIZE SQLITE_MAX_PAGE_SIZE
　　#endif
　　 
　　/*
　　** Ordinarily, if no value is explicitly provided, SQLite creates databases
　　** with page size SQLITE_DEFAULT_PAGE_SIZE. However, based on certain
　　** device characteristics (sector-size and atomic write() support),
　　** SQLite may choose a larger value. This constant is the maximum value
　　** SQLite will choose on its own.
　　*/
　　//数据库页面的最大默认大小
　　#ifndef SQLITE_MAX_DEFAULT_PAGE_SIZE
　　# define SQLITE_MAX_DEFAULT_PAGE_SIZE 8192
　　#endif
　　#if SQLITE_MAX_DEFAULT_PAGE_SIZE>SQLITE_MAX_PAGE_SIZE
　　# undef SQLITE_MAX_DEFAULT_PAGE_SIZE
　　# define SQLITE_MAX_DEFAULT_PAGE_SIZE SQLITE_MAX_PAGE_SIZE
　　#endif
　　 
　　 
　　/*
　　** Maximum number of pages in one database file.
　　**
　　** This is really just the default value for the max_page_count pragma.
　　** This value can be lowered (or raised) at run-time using that the
　　** max_page_count macro.
　　*/
　　//单个数据库文件的最大页数数
　　#ifndef SQLITE_MAX_PAGE_COUNT
　　# define SQLITE_MAX_PAGE_COUNT 1073741823
　　#endif
　　 
　　/*
　　** Maximum length (in bytes) of the pattern in a LIKE or GLOB
　　** operator.
　　*/
　　// LIKE or GLOB模式的最大长度（字节）
　　#ifndef SQLITE_MAX_LIKE_PATTERN_LENGTH
　　# define SQLITE_MAX_LIKE_PATTERN_LENGTH 50000
　　#endif
　　 
　　/*
　　** Maximum depth of recursion for triggers.
　　**
　　** A value of 1 means that a trigger program will not be able to itself
　　** fire any triggers. A value of 0 means that no trigger programs at all
　　** may be executed.
　　*/
　　//触发器程序的递归深度
　　#ifndef SQLITE_MAX_TRIGGER_DEPTH
　　# define SQLITE_MAX_TRIGGER_DEPTH 1000
　　#endif
　　//SQLITE限制参数定义完毕
　　/************** End of sqliteLimit.h *****************************************/
　　/************** Continuing where we left off in sqliteInt.h ******************/
　　//禁止Borland编译器的讨厌的警告
　　/* Disable nuisance warnings on Borland compilers */
　　#if defined(__BORLANDC__)
　　#pragma warn -rch /* unreachable code */
　　#pragma warn -ccc /* Condition is always true or false */
　　#pragma warn -aus /* Assigned value is never used */
　　#pragma warn -csu /* Comparing signed and unsigned */
　　#pragma warn -spa /* Suspicious pointer arithmetic */
　　#endif
　　//定义为GNU源码
　　/* Needed for various definitions... */
　　#ifndef _GNU_SOURCE
　　# define _GNU_SOURCE
　　#endif
　　 
　　/*
　　** Include standard header files as necessary
　　*/
　　//包含必要的头文件
　　#ifdef HAVE_STDINT_H
　　#include <stdint.h>
　　#endif
　　#ifdef HAVE_INTTYPES_H
　　#include <inttypes.h>
　　#endif
　　 
　　/*
　　** The number of samples of an index that SQLite takes in order to
　　** construct a histogram of the table content when running ANALYZE
　　** and with SQLITE_ENABLE_STAT2
　　*/
　　//索引样本数
　　#define SQLITE_INDEX_SAMPLES 10
　　 
　　/*
　　** The following macros are used to cast pointers to integers and
　　** integers to pointers.  The way you do this varies from one compiler
　　** to the next, so we have developed the following set of #if statements
　　** to generate appropriate macros for a wide range of compilers.
　　**
　　** The correct "ANSI" way to do this is to use the intptr_t type.
　　** Unfortunately, that typedef is not available on all compilers, or
　　** if it is available, it requires an #include of specific headers
　　** that very from one machine to the next.
　　**
　　** Ticket #3860:  The llvm-gcc-4.2 compiler from Apple chokes on
　　** the ((void*)&((char*)0)[X]) construct.  But MSVC chokes on ((void*)(X)).
　　** So we have to define the macros in different ways depending on the
　　** compiler.
　　*/
　　//下列宏完成指针转整数和整数转指针
　　#if defined(__PTRDIFF_TYPE__)  /* This case should work for GCC */
　　# define SQLITE_INT_TO_PTR(X)  ((void*)(__PTRDIFF_TYPE__)(X))
　　# define SQLITE_PTR_TO_INT(X)  ((int)(__PTRDIFF_TYPE__)(X))
　　#elif !defined(__GNUC__)       /* Works for compilers other than LLVM */
　　# define SQLITE_INT_TO_PTR(X)  ((void*)&((char*)0)[X])
　　# define SQLITE_PTR_TO_INT(X)  ((int)(((char*)X)-(char*)0))
　　#elif defined(HAVE_STDINT_H)   /* Use this case if we have ANSI headers */
　　# define SQLITE_INT_TO_PTR(X)  ((void*)(intptr_t)(X))
　　# define SQLITE_PTR_TO_INT(X)  ((int)(intptr_t)(X))
　　#else                          /* Generates a warning - but it always works */
　　# define SQLITE_INT_TO_PTR(X)  ((void*)(X))
　　# define SQLITE_PTR_TO_INT(X)  ((int)(X))
　　#endif
　　 
　　/*
　　** The SQLITE_THREADSAFE macro must be defined as either 0 or 1.
　　** Older versions of SQLite used an optional THREADSAFE macro.
　　** We support that for legacy
　　*/
　　// SQLITE_THREADSAFE线程安全宏被定义为0或1,
　　#if !defined(SQLITE_THREADSAFE)
　　#if defined(THREADSAFE)
　　# define SQLITE_THREADSAFE THREADSAFE
　　#else
　　# define SQLITE_THREADSAFE 1
　　#endif
　　#endif
　　 
　　/*
　　** The SQLITE_DEFAULT_MEMSTATUS macro must be defined as either 0 or 1.
　　** It determines whether or not the features related to
　　** SQLITE_CONFIG_MEMSTATUS are available by default or not. This value can
　　** be overridden at runtime using the sqlite3_config() API.
　　*/
　　// SQLITE_DEFAULT_MEMSTATUS宏被定义为0或1，在运行时可使
　　//用sqlite3_config() API修改该值
　　#if !defined(SQLITE_DEFAULT_MEMSTATUS)
　　# define SQLITE_DEFAULT_MEMSTATUS 1
　　#endif