76 lines
1.8 KiB
C
76 lines
1.8 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h> // This gives us sized types
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#include <stdbool.h>
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#include <assert.h>
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#define NB_NODES 4
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bool add_file(uint64_t* inodes, int file_size, char name[7]) {
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// We only have 7 bits for the file size, so it can't be bigger
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if (file_size > 0x7f || file_size < 0) {
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return false;
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}
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for (int i = 0; i < NB_NODES; i++) {
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bool is_taken = ((inodes[i] >> (7*8)) & 0x8) > 0;
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if (!is_taken) {
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// Set highest bit
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inodes[i] = ((uint64_t) file_size | 0x80) << (7*8);
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// Set name byte by byte
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for (int ii = 0; ii < 7; ii++) {
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inodes[i] |= (((uint64_t) name[ii]) & 0xff) << (ii*8);
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}
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return true;
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}
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}
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return false;
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}
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void printd_inodes(uint64_t* inodes) {
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printf("Debug with name: ");
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for (int i = 0; i < NB_NODES; i++) {
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for (int ii = 0; ii < 7; ii++) {
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// Get character out
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printf("%c", (uint8_t) ((inodes[i] >> (ii*8)) & 0xff));
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}
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printf(" %02x", (uint8_t) (inodes[i] >> (7*8)));
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if (i == NB_NODES - 1) {
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printf("\n");
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} else {
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printf(" ");
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}
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}
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}
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int main(void) {
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// Use bottom 8 bits for file size (7 bits) and occupied indicator (1 bit)
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// Use top 56 bits for 7 character name
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uint64_t* inodes = calloc(NB_NODES, sizeof(uint64_t));
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printd_inodes(inodes);
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add_file(inodes, 8, "one\0\0\0");
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printd_inodes(inodes);
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add_file(inodes, 12, "two\0\0\0");
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printd_inodes(inodes);
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assert(add_file(inodes, 121, "another"));
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printd_inodes(inodes);
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add_file(inodes, 127, "four\0\0");
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printd_inodes(inodes);
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FILE* f = fopen("bits.out", "wb");
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fwrite(inodes, sizeof(uint64_t), NB_NODES, f);
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fclose(f);
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free(inodes);
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}
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