SQLite开源代码分析（一） main函数里面有多少东西

最近在做物联网gateway，需要用到很多c语言知识。近期抽时间来看一下SQLite的源代码，来逐步分析一下人家的各种特性是怎么实现的。

也希望对自己的C代的基本功和提高有一些帮助吧。

代码版本：sqlite-amalgamation-3110100

以后就以这个版本为主要分析过程。

下载地址：http://www.sqlite.org/download.html

说明：一共四个文件，放在新建的VS工程中，既可以启动程序，并且出现SQLite的程序运行窗口，

然后就可以使用各种命令来进行相关的操作了。这个可以参考各种指导。

我这里主要就是分析各种功能是如何实现的。并且对源代码进行相关的说明。

该程序的启动函数是main函数。该函数代码如下：

int SQLITE_CDECL main(int argc, char **argv){

char *zErrMsg = 0;

ShellState data;

const char *zInitFile = 0;

int i;

int rc = 0;

int warnInmemoryDb = 0;

int readStdin = 1;

int nCmd = 0;

char **azCmd = 0;

#if USE_SYSTEM_SQLITE+0!=1

if( strcmp(sqlite3_sourceid(),SQLITE_SOURCE_ID)!=0 ){

utf8_printf(stderr, "SQLite header and source version mismatch\n%s\n%s\n",

sqlite3_sourceid(), SQLITE_SOURCE_ID);

exit(1);

}

#endif

setBinaryMode(stdin);

setvbuf(stderr, 0, _IONBF, 0); /* Make sure stderr is unbuffered */

Argv0 = argv[0];

main_init(&data);

stdin_is_interactive = isatty(0);

stdout_is_console = isatty(1);

/* Make sure we have a valid signal handler early, before anything

** else is done.

*/

#ifdef SIGINT

signal(SIGINT, interrupt_handler);

#endif

#ifdef SQLITE_SHELL_DBNAME_PROC

{

/* If the SQLITE_SHELL_DBNAME_PROC macro is defined, then it is the name

** of a C-function that will provide the name of the database file. Use

** this compile-time option to embed this shell program in larger

** applications. */

extern void SQLITE_SHELL_DBNAME_PROC(const char**);

SQLITE_SHELL_DBNAME_PROC(&data.zDbFilename);

warnInmemoryDb = 0;

}

#endif

/* Do an initial pass through the command-line argument to locate

** the name of the database file, the name of the initialization file,

** the size of the alternative malloc heap,

** and the first command to execute.

*/

for(i=1; i<argc; i++){

char *z;

z = argv[i];

if( z[0]!='-' ){

if( data.zDbFilename==0 ){

data.zDbFilename = z;

}else{

/* Excesss arguments are interpreted as SQL (or dot-commands) and

** mean that nothing is read from stdin */

readStdin = 0;

nCmd++;

azCmd = realloc(azCmd, sizeof(azCmd[0])*nCmd);

if( azCmd==0 ){

raw_printf(stderr, "out of memory\n");

exit(1);

}

azCmd[nCmd-1] = z;

}

}

if( z[1]=='-' ) z++;

if( strcmp(z,"-separator")==0

|| strcmp(z,"-nullvalue")==0

|| strcmp(z,"-newline")==0

|| strcmp(z,"-cmd")==0

){

(void)cmdline_option_value(argc, argv, ++i);

}else if( strcmp(z,"-init")==0 ){

zInitFile = cmdline_option_value(argc, argv, ++i);

}else if( strcmp(z,"-batch")==0 ){

/* Need to check for batch mode here to so we can avoid printing

** informational messages (like from process_sqliterc) before

** we do the actual processing of arguments later in a second pass.

*/

stdin_is_interactive = 0;

}else if( strcmp(z,"-heap")==0 ){

#if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)

const char *zSize;

sqlite3_int64 szHeap;

zSize = cmdline_option_value(argc, argv, ++i);

szHeap = integerValue(zSize);

if( szHeap>0x7fff0000 ) szHeap = 0x7fff0000;

sqlite3_config(SQLITE_CONFIG_HEAP, malloc((int)szHeap), (int)szHeap, 64);

#endif

}else if( strcmp(z,"-scratch")==0 ){

int n, sz;

sz = (int)integerValue(cmdline_option_value(argc,argv,++i));

if( sz>400000 ) sz = 400000;

if( sz<2500 ) sz = 2500;

n = (int)integerValue(cmdline_option_value(argc,argv,++i));

if( n>10 ) n = 10;

if( n<1 ) n = 1;

sqlite3_config(SQLITE_CONFIG_SCRATCH, malloc(n*sz+1), sz, n);

data.shellFlgs |= SHFLG_Scratch;

}else if( strcmp(z,"-pagecache")==0 ){

int n, sz;

sz = (int)integerValue(cmdline_option_value(argc,argv,++i));

if( sz>70000 ) sz = 70000;

if( sz<0 ) sz = 0;

n = (int)integerValue(cmdline_option_value(argc,argv,++i));

sqlite3_config(SQLITE_CONFIG_PAGECACHE,

(n>0 && sz>0) ? malloc(n*sz) : 0, sz, n);

data.shellFlgs |= SHFLG_Pagecache;

}else if( strcmp(z,"-lookaside")==0 ){

int n, sz;

sz = (int)integerValue(cmdline_option_value(argc,argv,++i));

if( sz<0 ) sz = 0;

n = (int)integerValue(cmdline_option_value(argc,argv,++i));

if( n<0 ) n = 0;

sqlite3_config(SQLITE_CONFIG_LOOKASIDE, sz, n);

if( sz*n==0 ) data.shellFlgs &= ~SHFLG_Lookaside;

#ifdef SQLITE_ENABLE_VFSTRACE

}else if( strcmp(z,"-vfstrace")==0 ){

extern int vfstrace_register(

const char *zTraceName,

const char *zOldVfsName,

int (*xOut)(const char*,void*),

void *pOutArg,

int makeDefault

);

vfstrace_register("trace",0,(int(*)(const char*,void*))fputs,stderr,1);

#endif

#ifdef SQLITE_ENABLE_MULTIPLEX

}else if( strcmp(z,"-multiplex")==0 ){

extern int sqlite3_multiple_initialize(const char*,int);

sqlite3_multiplex_initialize(0, 1);

#endif

}else if( strcmp(z,"-mmap")==0 ){

sqlite3_int64 sz = integerValue(cmdline_option_value(argc,argv,++i));

sqlite3_config(SQLITE_CONFIG_MMAP_SIZE, sz, sz);

}else if( strcmp(z,"-vfs")==0 ){

sqlite3_vfs *pVfs = sqlite3_vfs_find(cmdline_option_value(argc,argv,++i));

if( pVfs ){

sqlite3_vfs_register(pVfs, 1);

}else{

utf8_printf(stderr, "no such VFS: \"%s\"\n", argv[i]);

exit(1);

}

}

}

if( data.zDbFilename==0 ){

#ifndef SQLITE_OMIT_MEMORYDB

data.zDbFilename = ":memory:";

warnInmemoryDb = argc==1;

#else

utf8_printf(stderr,"%s: Error: no database filename specified\n", Argv0);

return 1;

#endif

}

data.out = stdout;

/* Go ahead and open the database file if it already exists. If the

** file does not exist, delay opening it. This prevents empty database

** files from being created if a user mistypes the database name argument

** to the sqlite command-line tool.

*/

if( access(data.zDbFilename, 0)==0 ){

open_db(&data, 0);

}

/* Process the initialization file if there is one. If no -init option

** is given on the command line, look for a file named ~/.sqliterc and

** try to process it.

*/

process_sqliterc(&data,zInitFile);

/* Make a second pass through the command-line argument and set

** options. This second pass is delayed until after the initialization

** file is processed so that the command-line arguments will override

** settings in the initialization file.

*/

for(i=1; i<argc; i++){

char *z = argv[i];

if( z[0]!='-' ) continue;

if( z[1]=='-' ){ z++; }

if( strcmp(z,"-init")==0 ){

i++;

}else if( strcmp(z,"-html")==0 ){

data.mode = MODE_Html;

}else if( strcmp(z,"-list")==0 ){

data.mode = MODE_List;

}else if( strcmp(z,"-line")==0 ){

data.mode = MODE_Line;

}else if( strcmp(z,"-column")==0 ){

data.mode = MODE_Column;

}else if( strcmp(z,"-csv")==0 ){

data.mode = MODE_Csv;

memcpy(data.colSeparator,",",2);

}else if( strcmp(z,"-ascii")==0 ){

data.mode = MODE_Ascii;

sqlite3_snprintf(sizeof(data.colSeparator), data.colSeparator,

SEP_Unit);

sqlite3_snprintf(sizeof(data.rowSeparator), data.rowSeparator,

SEP_Record);

}else if( strcmp(z,"-separator")==0 ){

sqlite3_snprintf(sizeof(data.colSeparator), data.colSeparator,

"%s",cmdline_option_value(argc,argv,++i));

}else if( strcmp(z,"-newline")==0 ){

sqlite3_snprintf(sizeof(data.rowSeparator), data.rowSeparator,

"%s",cmdline_option_value(argc,argv,++i));

}else if( strcmp(z,"-nullvalue")==0 ){

sqlite3_snprintf(sizeof(data.nullValue), data.nullValue,

"%s",cmdline_option_value(argc,argv,++i));

}else if( strcmp(z,"-header")==0 ){

data.showHeader = 1;

}else if( strcmp(z,"-noheader")==0 ){

data.showHeader = 0;

}else if( strcmp(z,"-echo")==0 ){

data.echoOn = 1;

}else if( strcmp(z,"-eqp")==0 ){

data.autoEQP = 1;

}else if( strcmp(z,"-stats")==0 ){

data.statsOn = 1;

}else if( strcmp(z,"-scanstats")==0 ){

data.scanstatsOn = 1;

}else if( strcmp(z,"-backslash")==0 ){

/* Undocumented command-line option: -backslash

** Causes C-style backslash escapes to be evaluated in SQL statements

** prior to sending the SQL into SQLite. Useful for injecting

** crazy bytes in the middle of SQL statements for testing and debugging.

*/

data.backslashOn = 1;

}else if( strcmp(z,"-bail")==0 ){

bail_on_error = 1;

}else if( strcmp(z,"-version")==0 ){

printf("%s %s\n", sqlite3_libversion(), sqlite3_sourceid());

return 0;

}else if( strcmp(z,"-interactive")==0 ){

stdin_is_interactive = 1;

}else if( strcmp(z,"-batch")==0 ){

stdin_is_interactive = 0;

}else if( strcmp(z,"-heap")==0 ){

i++;

}else if( strcmp(z,"-scratch")==0 ){

i+=2;

}else if( strcmp(z,"-pagecache")==0 ){

i+=2;

}else if( strcmp(z,"-lookaside")==0 ){

i+=2;

}else if( strcmp(z,"-mmap")==0 ){

i++;

}else if( strcmp(z,"-vfs")==0 ){

i++;

#ifdef SQLITE_ENABLE_VFSTRACE

}else if( strcmp(z,"-vfstrace")==0 ){

i++;

#endif

#ifdef SQLITE_ENABLE_MULTIPLEX

}else if( strcmp(z,"-multiplex")==0 ){

i++;

#endif

}else if( strcmp(z,"-help")==0 ){

usage(1);

}else if( strcmp(z,"-cmd")==0 ){

/* Run commands that follow -cmd first and separately from commands

** that simply appear on the command-line. This seems goofy. It would

** be better if all commands ran in the order that they appear. But

** we retain the goofy behavior for historical compatibility. */

if( i==argc-1 ) break;

z = cmdline_option_value(argc,argv,++i);

if( z[0]=='.' ){

rc = do_meta_command(z, &data);

if( rc && bail_on_error ) return rc==2 ? 0 : rc;

}else{

open_db(&data, 0);

rc = shell_exec(data.db, z, shell_callback, &data, &zErrMsg);

if( zErrMsg!=0 ){

utf8_printf(stderr,"Error: %s\n", zErrMsg);

if( bail_on_error ) return rc!=0 ? rc : 1;

}else if( rc!=0 ){

utf8_printf(stderr,"Error: unable to process SQL \"%s\"\n", z);

if( bail_on_error ) return rc;

}

}

}else{

utf8_printf(stderr,"%s: Error: unknown option: %s\n", Argv0, z);

raw_printf(stderr,"Use -help for a list of options.\n");

return 1;

}

data.cMode = data.mode;

}

if( !readStdin ){

/* Run all arguments that do not begin with '-' as if they were separate

** command-line inputs, except for the argToSkip argument which contains

** the database filename.

*/

for(i=0; i<nCmd; i++){

if( azCmd[i][0]=='.' ){

rc = do_meta_command(azCmd[i], &data);

if( rc ) return rc==2 ? 0 : rc;

}else{

open_db(&data, 0);

rc = shell_exec(data.db, azCmd[i], shell_callback, &data, &zErrMsg);

if( zErrMsg!=0 ){

utf8_printf(stderr,"Error: %s\n", zErrMsg);

return rc!=0 ? rc : 1;

}else if( rc!=0 ){

utf8_printf(stderr,"Error: unable to process SQL: %s\n", azCmd[i]);

return rc;

}

}

}

free(azCmd);

}else{

/* Run commands received from standard input

*/

if( stdin_is_interactive ){

char *zHome;

char *zHistory = 0;

int nHistory;

printf(

"SQLite version %s %.19s\n" /*extra-version-info*/

"Enter \".help\" for usage hints.\n",

sqlite3_libversion(), sqlite3_sourceid()

);

if( warnInmemoryDb ){

printf("Connected to a ");

printBold("transient in-memory database");

printf(".\nUse \".open FILENAME\" to reopen on a "

"persistent database.\n");

}

zHome = find_home_dir();

if( zHome ){

nHistory = strlen30(zHome) + 20;

if( (zHistory = malloc(nHistory))!=0 ){

sqlite3_snprintf(nHistory, zHistory,"%s/.sqlite_history", zHome);

}

}

if( zHistory ){ shell_read_history(zHistory); }

rc = process_input(&data, 0);

if( zHistory ){

shell_stifle_history(100);

shell_write_history(zHistory);

free(zHistory);

}

}else{

rc = process_input(&data, stdin);

}

}

set_table_name(&data, 0);

if( data.db ){

sqlite3_close(data.db);

}

sqlite3_free(data.zFreeOnClose);

return rc;

}