vfs testbench

tb/Makefile

@@ -0,0 +1,8 @@
+CC := gcc
+
+CFLAGS := -O3 -mno-red-zone -lm
+
+
+vfs:
+	$(CC) vfs_tb.c -o vfs_tb.elf $(CFLAGS)
+	./vfs_tb.elf

tb/vfs_tb.c

@@ -0,0 +1,162 @@
+#include "../kernel/lib/string.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <math.h>
+
+
+static int is_absolute(const char *path)
+{
+    return path[0] == '/';
+}
+
+static void simplify_path(char* dst, const char* src) {
+    
+    char *buf = malloc(strlen(src)+1);
+    
+
+    *dst = 0; 
+
+    strcpy(buf, src);
+
+    char *sub = strtok(buf, "/");
+
+    // each loop concatenates
+    // "/str"
+    // so the final output path is in format:
+    // "/foo/bar/foobar"
+    while (sub != NULL)
+    {
+
+        if(!strcmp(sub, "."))
+            ;
+        else if(!strcmp(sub, "..")) {
+            char* ptr = (char*)strrchr(dst, '/');
+
+            if(ptr != NULL)
+                *ptr = '\0';
+        }
+        else {
+            strcat(dst, "/");
+            strcat(dst, sub);
+        }
+
+        sub = strtok(NULL, "/");
+    }
+
+    free(buf);
+
+    if(dst[0] == '\0') {
+        *dst++ = '/';
+        *dst = '\0';
+    }
+}
+
+
+
+uint16_t path_hash(const char* path) {
+    unsigned len = strlen(path);
+    uint16_t res = 0;
+    const uint8_t* dwp = path;
+
+
+    for(unsigned i = 0; i < len; i += 1)
+    {
+        uint32_t entropy_bits = dwp[2*i] ^ (dwp[2*i+1] << 4);
+
+        entropy_bits ^= (entropy_bits << 4);
+
+        res = (res ^ (entropy_bits+i)) & 8191;
+    }
+    return res;
+}
+
+#define CACHE_SIZE 8192
+
+int main(void) {
+    /*
+    char* path[] = {
+        "//..//../././..///./home//mathieu//",
+        "",
+        "/../",
+        "/..///..//../././..///./home//mathieu////..//../././..///./home//mathieu////..//../././..///./home//mathieu//",
+        "/aaa/bbb/ccc/../cc/../jeu/../../../oui",
+        "/aaa/bbb/ccc/../cc/../jeu/./oui/",
+        "/oui/non",
+    };
+
+    for(int i = 0; i  < sizeof(path)/sizeof(char*); i++) {
+        char* buf = malloc(strlen(path[i])+1);
+        simplify_path(buf, path[i]);
+        printf("'%s' -> '%s' %d\n", path[i], buf, sizeof(path));
+
+        free(buf);
+    }*/
+
+    FILE* file = fopen("file_list.txt", "r");
+    char path[4097];
+
+    uint32_t cache[CACHE_SIZE];
+    uint64_t n_paths = 0;
+
+    int avlen = 0;
+
+
+    memset(cache, 0, CACHE_SIZE * sizeof(uint32_t));
+
+    while(fgets(path, 4096, file) != NULL) {
+        assert(strchr(path, '\n'));
+        *(char*)strchr(path, '\n') = '\0';
+
+        uint16_t hash = path_hash(path) & (CACHE_SIZE-1);
+
+        
+        if(hash >= CACHE_SIZE) {
+            printf("ayao %u\n", hash);
+            return 1;
+        }
+
+        int len = strlen(path)+1;
+
+        if(len & ~31)
+            len = (len & ~31) + 32;
+
+        avlen += len;
+
+        n_paths++;
+
+
+        cache[hash]++;
+    }
+    fclose(file);
+
+    int n_empty = 0;
+
+    unsigned min = 0xffffffff, max = 0;
+    double var = 0;
+    double e = n_paths / CACHE_SIZE;
+
+    
+    for(int i = 0; i < CACHE_SIZE; i++) { 
+        int x = cache[i];
+        if(!x)
+            n_empty++;
+
+        if(x < min)
+            min = x;
+        else if(x > max)
+            max = x;
+        
+        
+        var += (x - e) * (x - e);
+    }
+
+    int collisions = n_empty + n_paths - CACHE_SIZE;
+
+    var = sqrt(var / n_paths);
+
+    printf("min = %u, max = %u, V = %lf, total = %u, empty: %u "
+            "; path average len = %u, collision rate: %.2lf %%\n", 
+min,max,var,n_paths, n_empty, avlen / n_paths, collisions / (double)n_paths * 100.0);
+}