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// Written by retoor@molodetz.nl
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// This code provides a mechanism to initialize and manage file-backed memory using memory mapping and file operations for storing large
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// data sets temporarily in a file system.
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// The code uses `fcntl.h`, `stdbool.h`, `stdio.h`, `stdlib.h`, `string.h`, `sys/mman.h`, and `unistd.h` for file handling, memory
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// management, and basic input/output operations.
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// MIT License
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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#include <fcntl.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <unistd.h>
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typedef struct rfm_t {
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char path[4096];
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void *data;
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size_t size;
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long ptr;
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FILE *f;
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int fd;
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} rfm_t;
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rfm_t rfm;
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bool initialized = false;
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void rfm_destroy(rfm_t *r) {
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if (munmap(r->data, r->size) == -1) {
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perror("munmap");
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exit(EXIT_FAILURE);
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}
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close(r->fd);
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}
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void *falloc(size_t s) {
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rfm_t *rr = &rfm;
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char *data = (char *)rr->data + rfm.ptr;
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rfm.ptr += s;
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return data;
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}
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void *finit(char *path, size_t size) {
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if (!initialized) {
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initialized = true;
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memset(&rfm, 0, sizeof(rfm_t));
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rfm.size = size;
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if (path) {
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strcpy(rfm.path, path);
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rfm.fd = open(path, O_RDWR);
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} else {
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rfm.f = tmpfile();
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rfm.fd = fileno(rfm.f);
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}
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rfm.data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, rfm.fd, 0);
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}
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}
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int main() {
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finit("tast.dat", 1024 * 1024 * 100);
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char *data = (char *)falloc(10);
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strcpy(data, "ab");
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char *data2 = (char *)falloc(30);
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strcpy(data2, "ff\n");
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printf("%s\n", data);
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return 0;
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} |