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Move blockmem implementation out of the main raftable module.
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4 files changed

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‎contrib/raftable/blockmem.c

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#include "blockmem.h"
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#include <stddef.h>
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#include <assert.h>
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#include <stdbool.h>
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#include <string.h>
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#define BLOCK_LEN (256)
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#define BLOCK_DATA_LEN ((BLOCK_LEN) - offsetof(block_t, data))
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#define META(ORIGIN) ((meta_t *)(ORIGIN))
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#define BLOCK(ORIGIN, ID) ((block_t *)((char *)(ORIGIN) + BLOCK_LEN * ID))
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#define TAIL(ORIGIN, ID) (BLOCK(ORIGIN, ID)->next)
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#define USED(ORIGIN, ID) (BLOCK(ORIGIN, ID)->used)
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#define LEN(ORIGIN, ID) (BLOCK(ORIGIN, ID)->len)
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#define DATA(ORIGIN, ID) (BLOCK(ORIGIN, ID)->data)
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#define FREE(ORIGIN) (META(ORIGIN)->freeblock)
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typedef struct meta_t
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{
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int freeblock; /* the id of first free block, or -1 if none */
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char data[1];
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} meta_t;
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typedef struct block_t
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{
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bool used;
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int next;
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int len;
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char data[1];
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} block_t;
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int
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blockmem_format(void *origin, size_t size)
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{
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block_t *block;
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meta_t *meta;
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int id;
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int blocks = (size - 1) / BLOCK_LEN;
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if (blocks <= 0) return 0;
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FREE(origin) = 1;
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for (id = 1; id <= blocks; id++)
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{
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USED(origin, id) = 0;
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TAIL(origin, id) = id + 1;
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}
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TAIL(origin, blocks) = 0; /* the last block has no tail */
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return 1;
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}
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static size_t
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block_fill(void *origin, int id, void *src, size_t len)
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{
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if (len > BLOCK_DATA_LEN)
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len = BLOCK_DATA_LEN;
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LEN(origin, id) = len;
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memcpy(DATA(origin, id), src, len);
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return len;
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}
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void
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block_clear(void *origin, int id)
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{
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TAIL(origin, id) = 0;
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USED(origin, id) = true;
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LEN(origin, id) = 0;
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}
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static int
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block_alloc(void *origin)
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{
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int newborn = FREE(origin);
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if (!newborn) return 0;
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FREE(origin) = TAIL(origin, newborn);
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block_clear(origin, newborn);
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return newborn;
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}
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static void
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block_free(void *origin, int id)
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{
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/* behead the victim, and repeat for the tail */
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while (id > 0)
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{
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int tail;
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assert(USED(origin, id));
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USED(origin, id) = false;
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tail = TAIL(origin, id);
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TAIL(origin, id) = FREE(origin);
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FREE(origin) = id;
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id = tail;
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}
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}
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int
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blockmem_put(void *origin, void *src, size_t len)
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{
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int head = 0;
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int id = 0;
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char *cursor = src;
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size_t bytesleft = len;
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while (bytesleft > 0)
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{
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int copied;
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int newid = block_alloc(origin);
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if (!newid) goto failure;
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copied = block_fill(origin, newid, cursor, bytesleft);
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cursor += copied;
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bytesleft -= copied;
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if (id)
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TAIL(origin, id) = newid;
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else
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head = newid;
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id = newid;
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}
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return head;
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failure:
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block_free(origin, head);
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return -1;
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}
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size_t
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blockmem_len(void *origin, int id)
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{
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size_t len = 0;
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while (id > 0)
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{
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assert(USED(origin, id));
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len += LEN(origin, id);
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id = TAIL(origin, id);
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}
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assert(len > 0);
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return len;
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}
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size_t
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blockmem_get(void *origin, int id, void *dst, size_t len)
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{
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size_t copied = 0;
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char *cursor = dst;
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while ((id > 0) && (copied < len))
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{
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size_t tocopy = LEN(origin, id);
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if (tocopy > len - copied)
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tocopy = len - copied;
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assert(tocopy > 0);
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assert(USED(origin, id));
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memcpy(cursor, DATA(origin, id), tocopy);
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copied += tocopy;
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cursor += tocopy;
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id = TAIL(origin, id);
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}
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return len;
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}
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void
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blockmem_forget(void *origin, int id)
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{
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block_free(origin, id);
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}

‎contrib/raftable/blockmem.h

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#ifndef BLOCKMEM_H
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#define BLOCKMEM_H
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#include <stdlib.h>
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/*
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* Formats the memory region of 'size' bytes starting at 'origin'. Use this
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* before any other functions related to blockmem. Returns 1 on success,
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* 0 otherwise.
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*/
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int blockmem_format(void *origin, size_t size);
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/*
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* Allocates blocks in the formatted region starting at 'origin' and stores
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* 'len' bytes from 'src' inside those blocks. Returns the id for later _get(),
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* _len() and _forget() operations. Returns 0 if not enough free blocks.
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*/
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int blockmem_put(void *origin, void *src, size_t len);
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/*
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* Returns the length of data identified by 'id' that was previously stored
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* with a call to _put().
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*/
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size_t blockmem_len(void *origin, int id);
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/*
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* Retrieves into 'dst' no more than 'len' bytes of data identified by 'id'
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* that were previously stored with a call to _put(). Returns the length of data
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* actually copied.
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*/
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size_t blockmem_get(void *origin, int id, void *dst, size_t len);
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/*
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* Frees the blocks occupied by data identified by 'id'.
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*/
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void blockmem_forget(void *origin, int id);
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#endif

‎contrib/raftable/test-blockmem.c

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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 "blockmem.h"
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#define BLOCKMEM_SIZE (1024 * 1024)
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#define TEST_SIZE (10000)
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int
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main()
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{
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int rc = EXIT_SUCCESS;
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void *origin = malloc(BLOCKMEM_SIZE);
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if (!blockmem_format(origin, BLOCKMEM_SIZE))
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{
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fprintf(stderr, "couldn't format the blockmem\n");
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rc = EXIT_FAILURE;
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}
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else
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{
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char *a, *b;
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int i, id;
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a = malloc(TEST_SIZE);
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b = malloc(TEST_SIZE);
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for (i = 0; i < TEST_SIZE; i++)
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{
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a[i] = rand() % ('z' - 'a' + 1) + 'a';
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b[i] = '\0';
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}
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a[TEST_SIZE - 1] = '\0';
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id = blockmem_put(origin, a, TEST_SIZE);
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i = blockmem_get(origin, id, b, TEST_SIZE);
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if (i != TEST_SIZE)
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{
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fprintf(stderr, "got %d instead of %d\n", i, TEST_SIZE);
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rc = EXIT_FAILURE;
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}
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if (strcmp(a, b))
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{
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fprintf(stderr, "did not get out what was put in\n");
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rc = EXIT_FAILURE;
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}
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free(b);
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free(a);
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free(origin);
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}
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if (rc == EXIT_SUCCESS)
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fprintf(stderr, "blockmem test ok\n");
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else
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fprintf(stderr, "blockmem test failed\n");
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return rc;
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}

‎contrib/raftable/test.sh

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#!/bin/sh
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CC=clang
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set -ex
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$CC -o test-blockmem test-blockmem.c blockmem.c
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./test-blockmem

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