os_map.c
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上传日期:2022-05-23
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文件大小:9k
- /*-
- * See the file LICENSE for redistribution information.
- *
- * Copyright (c) 1996-2002
- * Sleepycat Software. All rights reserved.
- */
- #include "db_config.h"
- #ifndef lint
- static const char revid[] = "$Id: os_map.c,v 11.38 2002/09/10 02:35:48 bostic Exp $";
- #endif /* not lint */
- #include "db_int.h"
- static int __os_map
- __P((DB_ENV *, char *, REGINFO *, DB_FH *, size_t, int, int, int, void **));
- static int __os_unique_name __P((char *, HANDLE, char *, size_t));
- /*
- * __os_r_sysattach --
- * Create/join a shared memory region.
- */
- int
- __os_r_sysattach(dbenv, infop, rp)
- DB_ENV *dbenv;
- REGINFO *infop;
- REGION *rp;
- {
- DB_FH fh;
- int is_system, ret;
- /*
- * Try to open/create the file. We DO NOT need to ensure that multiple
- * threads/processes attempting to simultaneously create the region are
- * properly ordered, our caller has already taken care of that.
- */
- if ((ret = __os_open(dbenv, infop->name,
- DB_OSO_DIRECT |
- F_ISSET(infop, REGION_CREATE_OK) ? DB_OSO_CREATE: 0,
- infop->mode, &fh)) != 0) {
- __db_err(dbenv, "%s: %s", infop->name, db_strerror(ret));
- return (ret);
- }
- /*
- * On Windows/9X, files that are opened by multiple processes do not
- * share data correctly. For this reason, the DB_SYSTEM_MEM flag is
- * implied for any application that does not specify the DB_PRIVATE
- * flag.
- */
- is_system = F_ISSET(dbenv, DB_ENV_SYSTEM_MEM) ||
- (!F_ISSET(dbenv, DB_ENV_PRIVATE) && __os_is_winnt() == 0);
- /*
- * Map the file in. If we're creating an in-system-memory region,
- * specify a segment ID (which is never used again) so that the
- * calling code writes out the REGENV_REF structure to the primary
- * environment file.
- */
- ret = __os_map(dbenv, infop->name, infop, &fh, rp->size,
- 1, is_system, 0, &infop->addr);
- if (ret == 0 && is_system == 1)
- rp->segid = 1;
- (void)__os_closehandle(dbenv, &fh);
- return (ret);
- }
- /*
- * __os_r_sysdetach --
- * Detach from a shared memory region.
- */
- int
- __os_r_sysdetach(dbenv, infop, destroy)
- DB_ENV *dbenv;
- REGINFO *infop;
- int destroy;
- {
- int ret, t_ret;
- if (infop->wnt_handle != NULL) {
- (void)CloseHandle(*((HANDLE*)(infop->wnt_handle)));
- __os_free(dbenv, infop->wnt_handle);
- }
- ret = !UnmapViewOfFile(infop->addr) ? __os_win32_errno() : 0;
- if (ret != 0)
- __db_err(dbenv, "UnmapViewOfFile: %s", strerror(ret));
- if (!F_ISSET(dbenv, DB_ENV_SYSTEM_MEM) && destroy) {
- if (F_ISSET(dbenv, DB_ENV_OVERWRITE))
- (void)__db_overwrite(dbenv, infop->name);
- if ((t_ret = __os_unlink(dbenv, infop->name)) != 0 && ret == 0)
- ret = t_ret;
- }
- return (ret);
- }
- /*
- * __os_mapfile --
- * Map in a shared memory file.
- */
- int
- __os_mapfile(dbenv, path, fhp, len, is_rdonly, addr)
- DB_ENV *dbenv;
- char *path;
- DB_FH *fhp;
- int is_rdonly;
- size_t len;
- void **addr;
- {
- /* If the user replaced the map call, call through their interface. */
- if (DB_GLOBAL(j_map) != NULL)
- return (DB_GLOBAL(j_map)(path, len, 0, is_rdonly, addr));
- return (__os_map(dbenv, path, NULL, fhp, len, 0, 0, is_rdonly, addr));
- }
- /*
- * __os_unmapfile --
- * Unmap the shared memory file.
- */
- int
- __os_unmapfile(dbenv, addr, len)
- DB_ENV *dbenv;
- void *addr;
- size_t len;
- {
- /* If the user replaced the map call, call through their interface. */
- if (DB_GLOBAL(j_unmap) != NULL)
- return (DB_GLOBAL(j_unmap)(addr, len));
- return (!UnmapViewOfFile(addr) ? __os_win32_errno() : 0);
- }
- /*
- * __os_unique_name --
- * Create a unique identifying name from a pathname (may be absolute or
- * relative) and/or a file descriptor.
- *
- * The name returned must be unique (different files map to different
- * names), and repeatable (same files, map to same names). It's not
- * so easy to do by name. Should handle not only:
- *
- * foo.bar == ./foo.bar == c:/whatever_path/foo.bar
- *
- * but also understand that:
- *
- * foo.bar == Foo.Bar (FAT file system)
- * foo.bar != Foo.Bar (NTFS)
- *
- * The best solution is to use the file index, found in the file
- * information structure (similar to UNIX inode #).
- *
- * When a file is deleted, its file index may be reused,
- * but if the unique name has not gone from its namespace,
- * we may get a conflict. So to ensure some tie in to the
- * original pathname, we also use the creation time and the
- * file basename. This is not a perfect system, but it
- * should work for all but anamolous test cases.
- *
- */
- static int
- __os_unique_name(orig_path, hfile, result_path, result_path_len)
- char *orig_path, *result_path;
- HANDLE hfile;
- size_t result_path_len;
- {
- BY_HANDLE_FILE_INFORMATION fileinfo;
- char *basename, *p;
- /*
- * In Windows, pathname components are delimited by '/' or '', and
- * if neither is present, we need to strip off leading drive letter
- * (e.g. c:foo.txt).
- */
- basename = strrchr(orig_path, '/');
- p = strrchr(orig_path, '\');
- if (basename == NULL || (p != NULL && p > basename))
- basename = p;
- if (basename == NULL)
- basename = strrchr(orig_path, ':');
- if (basename == NULL)
- basename = orig_path;
- else
- basename++;
- if (!GetFileInformationByHandle(hfile, &fileinfo))
- return (__os_win32_errno());
- (void)snprintf(result_path, result_path_len,
- "__db_shmem.%8.8lx.%8.8lx.%8.8lx.%8.8lx.%8.8lx.%s",
- fileinfo.dwVolumeSerialNumber,
- fileinfo.nFileIndexHigh,
- fileinfo.nFileIndexLow,
- fileinfo.ftCreationTime.dwHighDateTime,
- fileinfo.ftCreationTime.dwHighDateTime,
- basename);
- return (0);
- }
- /*
- * __os_map --
- * The mmap(2) function for Windows.
- */
- static int
- __os_map(dbenv, path, infop, fhp, len, is_region, is_system, is_rdonly, addr)
- DB_ENV *dbenv;
- REGINFO *infop;
- char *path;
- DB_FH *fhp;
- int is_region, is_system, is_rdonly;
- size_t len;
- void **addr;
- {
- HANDLE hMemory;
- REGENV *renv;
- int ret, use_pagefile;
- char shmem_name[MAXPATHLEN];
- void *pMemory;
- ret = 0;
- if (infop != NULL)
- infop->wnt_handle = NULL;
- use_pagefile = is_region && is_system;
- /*
- * If creating a region in system space, get a matching name in the
- * paging file namespace.
- */
- if (use_pagefile && (ret = __os_unique_name(
- path, fhp->handle, shmem_name, sizeof(shmem_name))) != 0)
- return (ret);
- /*
- * XXX
- * DB: We have not implemented copy-on-write here.
- *
- * XXX
- * DB: This code will fail if the library is ever compiled on a 64-bit
- * machine.
- *
- * XXX
- * If this is an region in system memory, let's try opening using the
- * OpenFileMapping() first. Why, oh why are we doing this?
- *
- * Well, we might be asking the OS for a handle to a pre-existing
- * memory section, or we might be the first to get here and want the
- * section created. CreateFileMapping() sounds like it will do both
- * jobs. But, not so. It seems to mess up making the commit charge to
- * the process. It thinks, incorrectly, that when we want to join a
- * previously existing section, that it should make a commit charge
- * for the whole section. In fact, there is no new committed memory
- * whatever. The call can fail if there is insufficient memory free
- * to handle the erroneous commit charge. So, we find that the bogus
- * commit is not made if we call OpenFileMapping(). So we do that
- * first, and only call CreateFileMapping() if we're really creating
- * the section.
- */
- hMemory = NULL;
- if (use_pagefile)
- hMemory = OpenFileMapping(
- is_rdonly ? FILE_MAP_READ : FILE_MAP_ALL_ACCESS,
- 0,
- shmem_name);
- if (hMemory == NULL)
- hMemory = CreateFileMapping(
- use_pagefile ? (HANDLE)-1 : fhp->handle,
- 0,
- is_rdonly ? PAGE_READONLY : PAGE_READWRITE,
- 0, (DWORD)len,
- use_pagefile ? shmem_name : NULL);
- if (hMemory == NULL) {
- ret = __os_win32_errno();
- __db_err(dbenv, "OpenFileMapping: %s", strerror(ret));
- return (ret);
- }
- pMemory = MapViewOfFile(hMemory,
- (is_rdonly ? FILE_MAP_READ : FILE_MAP_ALL_ACCESS), 0, 0, len);
- if (pMemory == NULL) {
- ret = __os_win32_errno();
- __db_err(dbenv, "MapViewOfFile: %s", strerror(ret));
- return (ret);
- }
- /*
- * XXX
- * It turns out that the kernel object underlying the named section
- * is reference counted, but that the call to MapViewOfFile() above
- * does NOT increment the reference count! So, if we close the handle
- * here, the kernel deletes the object from the kernel namespace.
- * When a second process comes along to join the region, the kernel
- * happily creates a new object with the same name, but completely
- * different identity. The two processes then have distinct isolated
- * mapped sections, not at all what was wanted. Not closing the handle
- * here fixes this problem. We carry the handle around in the region
- * structure so we can close it when unmap is called. Ignore malloc
- * errors, it just means we leak the memory.
- */
- if (use_pagefile && infop != NULL) {
- if (__os_malloc(dbenv,
- sizeof(HANDLE), &infop->wnt_handle) == 0)
- memcpy(infop->wnt_handle, &hMemory, sizeof(HANDLE));
- } else
- CloseHandle(hMemory);
- if (is_region) {
- /*
- * XXX
- * Windows/95 zeroes anonymous memory regions at last close.
- * This means that the backing file can exist and reference
- * the region, but the region itself is no longer initialized.
- * If the caller is capable of creating the region, update
- * the REGINFO structure so that they do so.
- */
- renv = (REGENV *)pMemory;
- if (renv->magic == 0) {
- if (F_ISSET(infop, REGION_CREATE_OK))
- F_SET(infop, REGION_CREATE);
- else {
- (void)UnmapViewOfFile(pMemory);
- pMemory = NULL;
- ret = EAGAIN;
- }
- }
- }
- *addr = pMemory;
- return (ret);
- }