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174 lines
3.9 KiB
Plaintext
174 lines
3.9 KiB
Plaintext
Rules for opening shared files
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==============================
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File is already open, with share set to none:
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Can not open again
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File is already open for reading, with read share:
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Can open for reading only, share must include read (can have write too)
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File is already open for reading, with write share:
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Can open for writing only, share must include read (can have write too)
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File is already open for reading, with read + write share:
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Can open for read, writing or both, share must include read (can have write too)
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File is already open for writing, with read share:
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Can open for reading only, share must include write (can have read too)
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File is already open for writing, with write share:
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Can open for writing only, share must include write (can have read too)
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File is already open for writing, with read + write share:
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Can open for reading, writing or both, share must include write (can have read too)
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File is already open for reading + writing, with read share:
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Can open for reading only, share must be read + write
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File is already open for reading + writing, with write share:
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Can open for for writing only, share must be read + write
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File is already open for reading + writing, with read + write share:
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Can open for read, writing or both, share must be read + write
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Executive Summary
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-----------------
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Second open must have access within first share, must set second share to at least first access
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Documenting code
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----------------
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#include <stdio.h>
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#include <windows.h>
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int access[] = {
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GENERIC_READ,
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GENERIC_WRITE,
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GENERIC_READ | GENERIC_WRITE
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};
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char *access_names[] = {
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"G_READ",
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"G_WRITE",
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"G_READ|G_WRITE"
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};
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int share[] = {
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FILE_SHARE_READ,
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FILE_SHARE_WRITE,
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FILE_SHARE_READ | FILE_SHARE_WRITE
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};
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char *share_names[] = {
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"SHARE_READ",
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"SHARE_WRITE",
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"SHARE_READ|SHARE_WRITE"
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};
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void lockfiles(int access1, int share1, int access2, int share2)
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{
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HANDLE h1, h2;
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BOOL ret;
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if (access2 == 0 && share2 == 0) {
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printf("\n");
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printf("%22.22s\n%22.22s", access_names[access1], share_names[share1]);
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}
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h1 = CreateFile("lockedfile",
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access[access1],
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share[share1],
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NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
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if (h1 == INVALID_HANDLE_VALUE) {
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printf("Open1 failed: %d\n", GetLastError());
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return;
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}
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h2 = CreateFile("lockedfile",
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access[access2],
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share[share2],
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NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
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if (h2 == INVALID_HANDLE_VALUE) {
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printf(" %4.4s", "");
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} else {
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printf(" %4.4s", "OK");
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CloseHandle(h2);
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}
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CloseHandle(h1);
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}
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int main(int argc, char **argv)
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{
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int i, j, k, l;
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printf("\t\t\t\t\t\t\tSecond Open\n");
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printf("%22.22s G_RE G_RE G_RE G_WR G_WR G_WR G_RW G_RW G_RW\n", "");
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printf("%22.22s S_RE S_WR S_RW S_RE S_WR S_RW S_RE S_WR S_RW", "First open --v ");
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for (i = 0; i < 3; i++) {
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for (j = 0; j < 3; j++) {
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for (k = 0; k < 3; k++) {
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for (l = 0; l < 3; l++) {
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lockfiles(i, j, k, l);
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}
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}
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}
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}
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return(0);
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}
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Code output
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-----------
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Second Open
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G_RE G_RE G_RE G_WR G_WR G_WR G_RW G_RW G_RW
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First open --v S_RE S_WR S_RW S_RE S_WR S_RW S_RE S_WR S_RW
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G_READ
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SHARE_READ OK OK
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G_READ
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SHARE_WRITE OK OK
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G_READ
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SHARE_READ|SHARE_WRITE OK OK OK OK OK OK
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G_WRITE
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SHARE_READ OK OK
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G_WRITE
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SHARE_WRITE OK OK
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G_WRITE
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SHARE_READ|SHARE_WRITE OK OK OK OK OK OK
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G_READ|G_WRITE
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SHARE_READ OK
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G_READ|G_WRITE
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SHARE_WRITE OK
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G_READ|G_WRITE
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SHARE_READ|SHARE_WRITE OK OK OK
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