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| 1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ | |
| 2 /* This Source Code Form is subject to the terms of the Mozilla Public | |
| 3 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 5 | |
| 6 /* | |
| 7 ** prshm.h -- NSPR Shared Memory | |
| 8 ** | |
| 9 ** NSPR Named Shared Memory API provides a cross-platform named | |
| 10 ** shared-memory interface. NSPR Named Shared Memory is modeled on | |
| 11 ** similar constructs in Unix and Windows operating systems. Shared | |
| 12 ** memory allows multiple processes to access one or more common shared | |
| 13 ** memory regions, using it as an inter-process communication channel. | |
| 14 ** | |
| 15 ** Notes on Platform Independence: | |
| 16 ** NSPR Named Shared Memory is built on the native services offered | |
| 17 ** by most platforms. The NSPR Named Shared Memory API tries to | |
| 18 ** provide a least common denominator interface so that it works | |
| 19 ** across all supported platforms. To ensure that it works everywhere, | |
| 20 ** some platform considerations must be accomodated and the protocol | |
| 21 ** for using NSPR Shared Memory API must be observed. | |
| 22 ** | |
| 23 ** Protocol: | |
| 24 ** Multiple shared memories can be created using NSPR's Shared Memory | |
| 25 ** feature. For each named shared memory, as defined by the name | |
| 26 ** given in the PR_OpenSharedMemory() call, a protocol for using the | |
| 27 ** shared memory API is required to ensure desired behavior. Failing | |
| 28 ** to follow the protocol may yield unpredictable results. | |
| 29 ** | |
| 30 ** PR_OpenSharedMemory() will create the shared memory segment, if it | |
| 31 ** does not already exist, or open a connection that the existing | |
| 32 ** shared memory segment if it already exists. | |
| 33 ** | |
| 34 ** PR_AttachSharedMemory() should be called following | |
| 35 ** PR_OpenSharedMemory() to map the memory segment to an address in | |
| 36 ** the application's address space. | |
| 37 ** | |
| 38 ** PR_AttachSharedMemory() may be called to re-map a shared memory | |
| 39 ** segment after detaching the same PRSharedMemory object. Be | |
| 40 ** sure to detach it when done. | |
| 41 ** | |
| 42 ** PR_DetachSharedMemory() should be called to un-map the shared | |
| 43 ** memory segment from the application's address space. | |
| 44 ** | |
| 45 ** PR_CloseSharedMemory() should be called when no further use of the | |
| 46 ** PRSharedMemory object is required within a process. Following a | |
| 47 ** call to PR_CloseSharedMemory() the PRSharedMemory object is | |
| 48 ** invalid and cannot be reused. | |
| 49 ** | |
| 50 ** PR_DeleteSharedMemory() should be called before process | |
| 51 ** termination. After calling PR_DeleteSharedMemory() any further use | |
| 52 ** of the shared memory associated with the name may cause | |
| 53 ** unpredictable results. | |
| 54 ** | |
| 55 ** Files: | |
| 56 ** The name passed to PR_OpenSharedMemory() should be a valid filename | |
| 57 ** for a unix platform. PR_OpenSharedMemory() creates file using the | |
| 58 ** name passed in. Some platforms may mangle the name before creating | |
| 59 ** the file and the shared memory. | |
| 60 ** | |
| 61 ** The unix implementation may use SysV IPC shared memory, Posix | |
| 62 ** shared memory, or memory mapped files; the filename may used to | |
| 63 ** define the namespace. On Windows, the name is significant, but | |
| 64 ** there is no file associated with name. | |
| 65 ** | |
| 66 ** No assumptions about the persistence of data in the named file | |
| 67 ** should be made. Depending on platform, the shared memory may be | |
| 68 ** mapped onto system paging space and be discarded at process | |
| 69 ** termination. | |
| 70 ** | |
| 71 ** All names provided to PR_OpenSharedMemory() should be valid | |
| 72 ** filename syntax or name syntax for shared memory for the target | |
| 73 ** platform. Referenced directories should have permissions | |
| 74 ** appropriate for writing. | |
| 75 ** | |
| 76 ** Limits: | |
| 77 ** Different platforms have limits on both the number and size of | |
| 78 ** shared memory resources. The default system limits on some | |
| 79 ** platforms may be smaller than your requirements. These limits may | |
| 80 ** be adjusted on some platforms either via boot-time options or by | |
| 81 ** setting the size of the system paging space to accomodate more | |
| 82 ** and/or larger shared memory segment(s). | |
| 83 ** | |
| 84 ** Security: | |
| 85 ** On unix platforms, depending on implementation, contents of the | |
| 86 ** backing store for the shared memory can be exposed via the file | |
| 87 ** system. Set permissions and or access controls at create and attach | |
| 88 ** time to ensure you get the desired security. | |
| 89 ** | |
| 90 ** On windows platforms, no special security measures are provided. | |
| 91 ** | |
| 92 ** Example: | |
| 93 ** The test case pr/tests/nameshm1.c provides an example of use as | |
| 94 ** well as testing the operation of NSPR's Named Shared Memory. | |
| 95 ** | |
| 96 ** lth. 18-Aug-1999. | |
| 97 */ | |
| 98 | |
| 99 #ifndef prshm_h___ | |
| 100 #define prshm_h___ | |
| 101 | |
| 102 #include "prtypes.h" | |
| 103 #include "prio.h" | |
| 104 | |
| 105 PR_BEGIN_EXTERN_C | |
| 106 | |
| 107 /* | |
| 108 ** Declare opaque type PRSharedMemory. | |
| 109 */ | |
| 110 typedef struct PRSharedMemory PRSharedMemory; | |
| 111 | |
| 112 /* | |
| 113 ** FUNCTION: PR_OpenSharedMemory() | |
| 114 ** | |
| 115 ** DESCRIPTION: | |
| 116 ** PR_OpenSharedMemory() creates a new shared-memory segment or | |
| 117 ** associates a previously created memory segment with name. | |
| 118 ** | |
| 119 ** When parameter create is (PR_SHM_EXCL | PR_SHM_CREATE) and the | |
| 120 ** shared memory already exists, the function returns NULL with the | |
| 121 ** error set to PR_FILE_EXISTS_ERROR. | |
| 122 ** | |
| 123 ** When parameter create is PR_SHM_CREATE and the shared memory | |
| 124 ** already exists, a handle to that memory segment is returned. If | |
| 125 ** the segment does not exist, it is created and a pointer to the | |
| 126 ** related PRSharedMemory structure is returned. | |
| 127 ** | |
| 128 ** When parameter create is 0, and the shared memory exists, a | |
| 129 ** pointer to a PRSharedMemory is returned. If the shared memory does | |
| 130 ** not exist, NULL is returned with the error set to | |
| 131 ** PR_FILE_NOT_FOUND_ERROR. | |
| 132 ** | |
| 133 ** INPUTS: | |
| 134 ** name -- the name the shared-memory segment is known as. | |
| 135 ** size -- the size of the shared memory segment. | |
| 136 ** flags -- Options for creating the shared memory | |
| 137 ** mode -- Same as is passed to PR_Open() | |
| 138 ** | |
| 139 ** OUTPUTS: | |
| 140 ** The shared memory is allocated. | |
| 141 ** | |
| 142 ** RETURNS: Pointer to opaque structure PRSharedMemory or NULL. | |
| 143 ** NULL is returned on error. The reason for the error can be | |
| 144 ** retrieved via PR_GetError() and PR_GetOSError(); | |
| 145 ** | |
| 146 */ | |
| 147 NSPR_API( PRSharedMemory * ) | |
| 148 PR_OpenSharedMemory( | |
| 149 const char *name, | |
| 150 PRSize size, | |
| 151 PRIntn flags, | |
| 152 PRIntn mode | |
| 153 ); | |
| 154 /* Define values for PR_OpenShareMemory(...,create) */ | |
| 155 #define PR_SHM_CREATE 0x1 /* create if not exist */ | |
| 156 #define PR_SHM_EXCL 0x2 /* fail if already exists */ | |
| 157 | |
| 158 /* | |
| 159 ** FUNCTION: PR_AttachSharedMemory() | |
| 160 ** | |
| 161 ** DESCRIPTION: | |
| 162 ** PR_AttachSharedMemory() maps the shared-memory described by | |
| 163 ** shm to the current process. | |
| 164 ** | |
| 165 ** INPUTS: | |
| 166 ** shm -- The handle returned from PR_OpenSharedMemory(). | |
| 167 ** flags -- options for mapping the shared memory. | |
| 168 ** PR_SHM_READONLY causes the memory to be attached | |
| 169 ** read-only. | |
| 170 ** | |
| 171 ** OUTPUTS: | |
| 172 ** On success, the shared memory segment represented by shm is mapped | |
| 173 ** into the process' address space. | |
| 174 ** | |
| 175 ** RETURNS: Address where shared memory is mapped, or NULL. | |
| 176 ** NULL is returned on error. The reason for the error can be | |
| 177 ** retrieved via PR_GetError() and PR_GetOSError(); | |
| 178 ** | |
| 179 ** | |
| 180 */ | |
| 181 NSPR_API( void * ) | |
| 182 PR_AttachSharedMemory( | |
| 183 PRSharedMemory *shm, | |
| 184 PRIntn flags | |
| 185 ); | |
| 186 /* Define values for PR_AttachSharedMemory(...,flags) */ | |
| 187 #define PR_SHM_READONLY 0x01 | |
| 188 | |
| 189 /* | |
| 190 ** FUNCTION: PR_DetachSharedMemory() | |
| 191 ** | |
| 192 ** DESCRIPTION: | |
| 193 ** PR_DetachSharedMemory() detaches the shared-memory described | |
| 194 ** by shm. | |
| 195 ** | |
| 196 ** INPUTS: | |
| 197 ** shm -- The handle returned from PR_OpenSharedMemory(). | |
| 198 ** addr -- The address at which the memory was attached. | |
| 199 ** | |
| 200 ** OUTPUTS: | |
| 201 ** The shared memory mapped to an address via a previous call to | |
| 202 ** PR_AttachSharedMemory() is unmapped. | |
| 203 ** | |
| 204 ** RETURNS: PRStatus | |
| 205 ** | |
| 206 */ | |
| 207 NSPR_API( PRStatus ) | |
| 208 PR_DetachSharedMemory( | |
| 209 PRSharedMemory *shm, | |
| 210 void *addr | |
| 211 ); | |
| 212 | |
| 213 /* | |
| 214 ** FUNCTION: PR_CloseSharedMemory() | |
| 215 ** | |
| 216 ** DESCRIPTION: | |
| 217 ** PR_CloseSharedMemory() closes the shared-memory described by | |
| 218 ** shm. | |
| 219 ** | |
| 220 ** INPUTS: | |
| 221 ** shm -- The handle returned from PR_OpenSharedMemory(). | |
| 222 ** | |
| 223 ** OUTPUTS: | |
| 224 ** the shared memory represented by shm is closed | |
| 225 ** | |
| 226 ** RETURNS: PRStatus | |
| 227 ** | |
| 228 */ | |
| 229 NSPR_API( PRStatus ) | |
| 230 PR_CloseSharedMemory( | |
| 231 PRSharedMemory *shm | |
| 232 ); | |
| 233 | |
| 234 /* | |
| 235 ** FUNCTION: PR_DeleteSharedMemory() | |
| 236 ** | |
| 237 ** DESCRIPTION: | |
| 238 ** The shared memory resource represented by name is released. | |
| 239 ** | |
| 240 ** INPUTS: | |
| 241 ** name -- the name the shared-memory segment | |
| 242 ** | |
| 243 ** OUTPUTS: | |
| 244 ** depending on platform, resources may be returned to the underlying | |
| 245 ** operating system. | |
| 246 ** | |
| 247 ** RETURNS: PRStatus | |
| 248 ** | |
| 249 */ | |
| 250 NSPR_API( PRStatus ) | |
| 251 PR_DeleteSharedMemory( | |
| 252 const char *name | |
| 253 ); | |
| 254 | |
| 255 PR_END_EXTERN_C | |
| 256 | |
| 257 #endif /* prshm_h___ */ | |
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Chromium Code Reviews
Issue 2078763002:
Delete bundled copy of NSS and replace with README. (Closed)
Base URL: https://chromium.googlesource.com/chromium/deps/nss@master