mirror of
https://gitlab.com/cznic/sqlite.git
synced 2025-05-17 23:26:41 +00:00
326 lines
11 KiB
Go
326 lines
11 KiB
Go
// Copyright 2021 The Sqlite Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build !linux
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package sqlite3
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import (
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"fmt"
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"sync"
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"sync/atomic"
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"unsafe"
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"modernc.org/libc"
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"modernc.org/libc/sys/types"
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)
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func init() {
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tls := libc.NewTLS()
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if Xsqlite3_threadsafe(tls) == 0 {
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panic(fmt.Errorf("sqlite: thread safety configuration error"))
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}
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varArgs := libc.Xmalloc(tls, types.Size_t(unsafe.Sizeof(uintptr(0))))
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if varArgs == 0 {
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panic(fmt.Errorf("cannot allocate memory"))
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}
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// int sqlite3_config(int, ...);
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if rc := Xsqlite3_config(tls, SQLITE_CONFIG_MUTEX, libc.VaList(varArgs, uintptr(unsafe.Pointer(&mutexMethods)))); rc != SQLITE_OK {
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p := Xsqlite3_errstr(tls, rc)
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str := libc.GoString(p)
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panic(fmt.Errorf("sqlite: failed to configure mutex methods: %v", str))
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}
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libc.Xfree(tls, varArgs)
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tls.Close()
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}
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var (
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mutexMethods = Sqlite3_mutex_methods{
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FxMutexInit: *(*uintptr)(unsafe.Pointer(&struct{ f func(*libc.TLS) int32 }{mutexInit})),
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FxMutexEnd: *(*uintptr)(unsafe.Pointer(&struct{ f func(*libc.TLS) int32 }{mutexEnd})),
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FxMutexAlloc: *(*uintptr)(unsafe.Pointer(&struct {
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f func(*libc.TLS, int32) uintptr
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}{mutexAlloc})),
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FxMutexFree: *(*uintptr)(unsafe.Pointer(&struct{ f func(*libc.TLS, uintptr) }{mutexFree})),
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FxMutexEnter: *(*uintptr)(unsafe.Pointer(&struct{ f func(*libc.TLS, uintptr) }{mutexEnter})),
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FxMutexTry: *(*uintptr)(unsafe.Pointer(&struct {
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f func(*libc.TLS, uintptr) int32
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}{mutexTry})),
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FxMutexLeave: *(*uintptr)(unsafe.Pointer(&struct{ f func(*libc.TLS, uintptr) }{mutexLeave})),
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FxMutexHeld: *(*uintptr)(unsafe.Pointer(&struct {
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f func(*libc.TLS, uintptr) int32
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}{mutexHeld})),
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FxMutexNotheld: *(*uintptr)(unsafe.Pointer(&struct {
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f func(*libc.TLS, uintptr) int32
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}{mutexNotheld})),
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}
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mutexApp10 mutex
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mutexApp20 mutex
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mutexApp30 mutex
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mutexLRU0 mutex
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mutexMaster0 mutex
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mutexMem0 mutex
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mutexOpen0 mutex
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mutexPMem0 mutex
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mutexPRNG0 mutex
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mutexVFS10 mutex
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mutexVFS20 mutex
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mutexVFS30 mutex
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mutexApp1 = uintptr(unsafe.Pointer(&mutexApp10))
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mutexApp2 = uintptr(unsafe.Pointer(&mutexApp20))
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mutexApp3 = uintptr(unsafe.Pointer(&mutexApp30))
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mutexLRU = uintptr(unsafe.Pointer(&mutexLRU0))
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mutexMaster = uintptr(unsafe.Pointer(&mutexMaster0))
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mutexMem = uintptr(unsafe.Pointer(&mutexMem0))
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mutexOpen = uintptr(unsafe.Pointer(&mutexOpen0))
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mutexPMem = uintptr(unsafe.Pointer(&mutexPMem0))
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mutexPRNG = uintptr(unsafe.Pointer(&mutexPRNG0))
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mutexVFS1 = uintptr(unsafe.Pointer(&mutexVFS10))
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mutexVFS2 = uintptr(unsafe.Pointer(&mutexVFS20))
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mutexVFS3 = uintptr(unsafe.Pointer(&mutexVFS30))
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)
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type mutex struct {
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sync.Mutex
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cnt int32
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id int32 // tls.ID
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recursive bool
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}
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// int (*xMutexInit)(void);
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//
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// The xMutexInit method defined by this structure is invoked as part of system
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// initialization by the sqlite3_initialize() function. The xMutexInit routine
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// is called by SQLite exactly once for each effective call to
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// sqlite3_initialize().
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//
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// The xMutexInit() method must be threadsafe. It must be harmless to invoke
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// xMutexInit() multiple times within the same process and without intervening
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// calls to xMutexEnd(). Second and subsequent calls to xMutexInit() must be
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// no-ops. xMutexInit() must not use SQLite memory allocation (sqlite3_malloc()
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// and its associates).
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//
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// If xMutexInit fails in any way, it is expected to clean up after itself
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// prior to returning.
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func mutexInit(tls *libc.TLS) int32 { return SQLITE_OK }
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// int (*xMutexEnd)(void);
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func mutexEnd(tls *libc.TLS) int32 { return SQLITE_OK }
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// sqlite3_mutex *(*xMutexAlloc)(int);
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//
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// The sqlite3_mutex_alloc() routine allocates a new mutex and returns a
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// pointer to it. The sqlite3_mutex_alloc() routine returns NULL if it is
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// unable to allocate the requested mutex. The argument to
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// sqlite3_mutex_alloc() must one of these integer constants:
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//
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// SQLITE_MUTEX_FAST
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// SQLITE_MUTEX_RECURSIVE
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// SQLITE_MUTEX_STATIC_MASTER
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// SQLITE_MUTEX_STATIC_MEM
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// SQLITE_MUTEX_STATIC_OPEN
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// SQLITE_MUTEX_STATIC_PRNG
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// SQLITE_MUTEX_STATIC_LRU
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// SQLITE_MUTEX_STATIC_PMEM
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// SQLITE_MUTEX_STATIC_APP1
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// SQLITE_MUTEX_STATIC_APP2
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// SQLITE_MUTEX_STATIC_APP3
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// SQLITE_MUTEX_STATIC_VFS1
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// SQLITE_MUTEX_STATIC_VFS2
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// SQLITE_MUTEX_STATIC_VFS3
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//
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// The first two constants (SQLITE_MUTEX_FAST and SQLITE_MUTEX_RECURSIVE) cause
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// sqlite3_mutex_alloc() to create a new mutex. The new mutex is recursive when
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// SQLITE_MUTEX_RECURSIVE is used but not necessarily so when SQLITE_MUTEX_FAST
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// is used. The mutex implementation does not need to make a distinction
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// between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does not want to.
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// SQLite will only request a recursive mutex in cases where it really needs
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// one. If a faster non-recursive mutex implementation is available on the host
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// platform, the mutex subsystem might return such a mutex in response to
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// SQLITE_MUTEX_FAST.
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//
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// The other allowed parameters to sqlite3_mutex_alloc() (anything other than
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// SQLITE_MUTEX_FAST and SQLITE_MUTEX_RECURSIVE) each return a pointer to a
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// static preexisting mutex. Nine static mutexes are used by the current
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// version of SQLite. Future versions of SQLite may add additional static
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// mutexes. Static mutexes are for internal use by SQLite only. Applications
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// that use SQLite mutexes should use only the dynamic mutexes returned by
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// SQLITE_MUTEX_FAST or SQLITE_MUTEX_RECURSIVE.
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//
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// Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST or
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// SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc() returns a
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// different mutex on every call. For the static mutex types, the same mutex is
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// returned on every call that has the same type number.
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func mutexAlloc(tls *libc.TLS, typ int32) (r uintptr) {
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switch typ {
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case SQLITE_MUTEX_FAST:
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r = libc.Xcalloc(tls, 1, types.Size_t(unsafe.Sizeof(mutex{})))
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return r
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case SQLITE_MUTEX_RECURSIVE:
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r = libc.Xcalloc(tls, 1, types.Size_t(unsafe.Sizeof(mutex{})))
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(*mutex)(unsafe.Pointer(r)).recursive = true
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return r
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case SQLITE_MUTEX_STATIC_MASTER:
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return mutexMaster
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case SQLITE_MUTEX_STATIC_MEM:
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return mutexMem
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case SQLITE_MUTEX_STATIC_OPEN:
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return mutexOpen
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case SQLITE_MUTEX_STATIC_PRNG:
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return mutexPRNG
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case SQLITE_MUTEX_STATIC_LRU:
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return mutexLRU
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case SQLITE_MUTEX_STATIC_PMEM:
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return mutexPMem
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case SQLITE_MUTEX_STATIC_APP1:
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return mutexApp1
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case SQLITE_MUTEX_STATIC_APP2:
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return mutexApp2
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case SQLITE_MUTEX_STATIC_APP3:
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return mutexApp3
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case SQLITE_MUTEX_STATIC_VFS1:
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return mutexVFS1
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case SQLITE_MUTEX_STATIC_VFS2:
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return mutexVFS2
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case SQLITE_MUTEX_STATIC_VFS3:
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return mutexVFS3
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default:
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return 0
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}
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}
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// void (*xMutexFree)(sqlite3_mutex *);
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func mutexFree(tls *libc.TLS, m uintptr) {
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libc.Xfree(tls, m)
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}
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// The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt to enter
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// a mutex. If another thread is already within the mutex,
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// sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
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// SQLITE_BUSY. The sqlite3_mutex_try() interface returns SQLITE_OK upon
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// successful entry. Mutexes created using SQLITE_MUTEX_RECURSIVE can be
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// entered multiple times by the same thread. In such cases, the mutex must be
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// exited an equal number of times before another thread can enter. If the same
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// thread tries to enter any mutex other than an SQLITE_MUTEX_RECURSIVE more
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// than once, the behavior is undefined.
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//
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// If the argument to sqlite3_mutex_enter(), sqlite3_mutex_try(), or
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// sqlite3_mutex_leave() is a NULL pointer, then all three routines behave as
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// no-ops.
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// void (*xMutexEnter)(sqlite3_mutex *);
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func mutexEnter(tls *libc.TLS, m uintptr) {
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if m == 0 {
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return
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}
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if !(*mutex)(unsafe.Pointer(m)).recursive {
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(*mutex)(unsafe.Pointer(m)).Lock()
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(*mutex)(unsafe.Pointer(m)).id = tls.ID
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return
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}
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id := tls.ID
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if atomic.CompareAndSwapInt32(&(*mutex)(unsafe.Pointer(m)).id, 0, id) {
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(*mutex)(unsafe.Pointer(m)).cnt = 1
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(*mutex)(unsafe.Pointer(m)).Lock()
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return
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}
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if atomic.LoadInt32(&(*mutex)(unsafe.Pointer(m)).id) == id {
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(*mutex)(unsafe.Pointer(m)).cnt++
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return
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}
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for {
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(*mutex)(unsafe.Pointer(m)).Lock()
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if atomic.CompareAndSwapInt32(&(*mutex)(unsafe.Pointer(m)).id, 0, id) {
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(*mutex)(unsafe.Pointer(m)).cnt = 1
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return
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}
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(*mutex)(unsafe.Pointer(m)).Unlock()
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}
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}
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// int (*xMutexTry)(sqlite3_mutex *);
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func mutexTry(tls *libc.TLS, m uintptr) int32 {
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if m == 0 {
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return SQLITE_OK
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}
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if !(*mutex)(unsafe.Pointer(m)).recursive {
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if (*mutex)(unsafe.Pointer(m)).TryLock() {
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return SQLITE_OK
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}
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}
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return SQLITE_BUSY
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}
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// void (*xMutexLeave)(sqlite3_mutex *);
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func mutexLeave(tls *libc.TLS, m uintptr) {
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if m == 0 {
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return
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}
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if !(*mutex)(unsafe.Pointer(m)).recursive {
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(*mutex)(unsafe.Pointer(m)).id = 0
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(*mutex)(unsafe.Pointer(m)).Unlock()
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return
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}
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if atomic.AddInt32(&(*mutex)(unsafe.Pointer(m)).cnt, -1) == 0 {
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atomic.StoreInt32(&(*mutex)(unsafe.Pointer(m)).id, 0)
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(*mutex)(unsafe.Pointer(m)).Unlock()
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}
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}
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// The sqlite3_mutex_held() and sqlite3_mutex_notheld() routines are intended
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// for use inside assert() statements. The SQLite core never uses these
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// routines except inside an assert() and applications are advised to follow
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// the lead of the core. The SQLite core only provides implementations for
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// these routines when it is compiled with the SQLITE_DEBUG flag. External
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// mutex implementations are only required to provide these routines if
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// SQLITE_DEBUG is defined and if NDEBUG is not defined.
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//
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// These routines should return true if the mutex in their argument is held or
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// not held, respectively, by the calling thread.
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//
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// The implementation is not required to provide versions of these routines
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// that actually work. If the implementation does not provide working versions
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// of these routines, it should at least provide stubs that always return true
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// so that one does not get spurious assertion failures.
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//
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// If the argument to sqlite3_mutex_held() is a NULL pointer then the routine
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// should return 1. This seems counter-intuitive since clearly the mutex cannot
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// be held if it does not exist. But the reason the mutex does not exist is
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// because the build is not using mutexes. And we do not want the assert()
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// containing the call to sqlite3_mutex_held() to fail, so a non-zero return is
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// the appropriate thing to do. The sqlite3_mutex_notheld() interface should
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// also return 1 when given a NULL pointer.
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// int (*xMutexHeld)(sqlite3_mutex *);
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func mutexHeld(tls *libc.TLS, m uintptr) int32 {
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if m == 0 {
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return 1
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}
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return libc.Bool32(atomic.LoadInt32(&(*mutex)(unsafe.Pointer(m)).id) == tls.ID)
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}
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// int (*xMutexNotheld)(sqlite3_mutex *);
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func mutexNotheld(tls *libc.TLS, m uintptr) int32 {
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if m == 0 {
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return 1
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}
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return libc.Bool32(atomic.LoadInt32(&(*mutex)(unsafe.Pointer(m)).id) != tls.ID)
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}
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