Created little config parser

geky · geky · commit b113bba3ae2e · 2017-02-20T17:47:24.000-06:00
An odd start, but a start nonetheless
diff --git a/emu/cfg.c b/emu/cfg.c
@@ -0,0 +1,191 @@
+#include "cfg.h"
+
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+
+
+static int cfg_buffer(cfg_t *cfg, char c) {
+    // Amortize double
+    if (cfg->blen == cfg->bsize) {
+        size_t nsize = cfg->bsize * 2;
+        char *nbuf = malloc(nsize);
+        if (!nbuf) {
+            return -ENOMEM;
+        }
+
+        memcpy(nbuf, cfg->buf, cfg->bsize);
+        free(cfg->buf);
+        cfg->buf = nbuf;
+        cfg->bsize = nsize;
+    }
+
+    cfg->buf[cfg->blen] = c;
+    cfg->blen += 1;
+    return 0;
+}
+
+static int cfg_attr(cfg_t *cfg, unsigned key, unsigned val) {
+    // Amortize double
+    if (cfg->len == cfg->size) {
+        size_t nsize = cfg->size * 2;
+        struct cfg_attr *nattrs = malloc(nsize*sizeof(struct cfg_attr));
+        if (!nattrs) {
+            return -ENOMEM;
+        }
+
+        memcpy(nattrs, cfg->attrs, cfg->size*sizeof(struct cfg_attr));
+        free(cfg->attrs);
+        cfg->attrs = nattrs;
+        cfg->size = nsize;
+    }
+
+    // Keep attrs sorted for binary search
+    unsigned i = 0;
+    while (i < cfg->len &&
+            strcmp(&cfg->buf[key],
+                &cfg->buf[cfg->attrs[i].key]) > 0) {
+        i += 1;
+    }
+
+    memmove(&cfg->attrs[i+1], &cfg->attrs[i],
+        (cfg->size - i)*sizeof(struct cfg_attr));
+    cfg->attrs[i].key = key;
+    cfg->attrs[i].val = val;
+    cfg->len += 1;
+    return 0;
+}
+
+static bool cfg_match(FILE *f, const char *matches) {
+    char c = getc(f);
+    ungetc(c, f);
+
+    for (int i = 0; matches[i]; i++) {
+        if (c == matches[i]) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+int cfg_create(cfg_t *cfg, const char *filename) {
+    // start with some initial space
+    cfg->len = 0;
+    cfg->size = 4;
+    cfg->attrs = malloc(cfg->size*sizeof(struct cfg_attr));
+
+    cfg->blen = 0;
+    cfg->bsize = 16;
+    cfg->buf = malloc(cfg->size);
+
+    FILE *f = fopen(filename, "r");
+    if (!f) {
+        return -errno;
+    }
+
+    while (!feof(f)) {
+        int err;
+
+        while (cfg_match(f, " \t\v\f")) {
+            fgetc(f);
+        }
+
+        if (!cfg_match(f, "#\r\n")) {
+            unsigned key = cfg->blen;
+            while (!cfg_match(f, " \t\v\f:#") && !feof(f)) {
+                if ((err = cfg_buffer(cfg, fgetc(f)))) {
+                    return err;
+                }
+            }
+            if ((err = cfg_buffer(cfg, 0))) {
+                return err;
+            }
+
+            while (cfg_match(f, " \t\v\f")) {
+                fgetc(f);
+            }
+
+            if (cfg_match(f, ":")) {
+                fgetc(f);
+                while (cfg_match(f, " \t\v\f")) {
+                    fgetc(f);
+                }
+
+                unsigned val = cfg->blen;
+                while (!cfg_match(f, " \t\v\f#\r\n") && !feof(f)) {
+                    if ((err = cfg_buffer(cfg, fgetc(f)))) {
+                        return err;
+                    }
+                }
+                if ((err = cfg_buffer(cfg, 0))) {
+                    return err;
+                }
+
+                if ((err = cfg_attr(cfg, key, val))) {
+                    return err;
+                }
+            } else {
+                cfg->blen = key;
+            }
+        }
+
+        while (!cfg_match(f, "\r\n") && !feof(f)) {
+            fgetc(f);
+        }
+        fgetc(f);
+    }
+
+    return 0;
+}
+
+void cfg_destroy(cfg_t *cfg) {
+    free(cfg->attrs);
+}
+
+bool cfg_has(cfg_t *cfg, const char *key) {
+    return cfg_get(cfg, key, 0);
+}
+
+const char *cfg_get(cfg_t *cfg, const char *key, const char *def) {
+    // binary search for attribute
+    int lo = 0;
+    int hi = cfg->len-1;
+
+    while (lo <= hi) {
+        int i = (hi + lo) / 2;
+        int cmp = strcmp(key, &cfg->buf[cfg->attrs[i].key]);
+        if (cmp == 0) {
+            return &cfg->buf[cfg->attrs[i].val];
+        } else if (cmp < 0) {
+            hi = i-1;
+        } else {
+            lo = i+1;
+        }
+    }
+
+    return def;
+}
+
+ssize_t cfg_geti(cfg_t *cfg, const char *key, ssize_t def) {
+    const char *val = cfg_get(cfg, key, 0);
+    if (!val) {
+        return def;
+    }
+
+    char *end;
+    ssize_t res = strtoll(val, &end, 0);
+    return (end == val) ? def : res;
+}
+
+size_t cfg_getu(cfg_t *cfg, const char *key, size_t def) {
+    const char *val = cfg_get(cfg, key, 0);
+    if (!val) {
+        return def;
+    }
+
+    char *end;
+    size_t res = strtoull(val, &end, 0);
+    return (end == val) ? def : res;
+}
diff --git a/emu/cfg.h b/emu/cfg.h
@@ -0,0 +1,74 @@
+/*
+ * Simple config parser
+ *
+ * Copyright (c) 2016 Christopher Haster
+ * Distributed under the MIT license
+ */
+#ifndef CFG_H
+#define CFG_H
+
+#include <stddef.h>
+#include <stdbool.h>
+#include <unistd.h>
+
+// This is a simple parser for config files
+//
+// The cfg file format is dumb simple. Attributes are
+// key value pairs separated by a single colon. Delimited
+// by comments (#) and newlines (\r\n) and trims
+// whitespace ( \t\v\f)
+//
+// Here's an example file
+// # Here is a dump example
+// looky: it's_an_attribute
+// hey_look: another_attribute
+//
+// huh: yeah_that's_basically_it # basically it
+
+// Internal config structure
+typedef struct cfg {
+    size_t len;
+    size_t size;
+
+    size_t blen;
+    size_t bsize;
+    char *buf;
+
+    struct cfg_attr {
+        unsigned key;
+        unsigned val;
+    } *attrs;
+} cfg_t;
+
+
+
+// Creates a cfg object and reads in the cfg file from the filename
+//
+// If the cfg_read fails, returns a negative value from the underlying
+// stdio functions
+int cfg_create(cfg_t *cfg, const char *filename);
+
+// Destroys the cfg object and frees any used memory
+void cfg_destroy(cfg_t *cfg);
+
+// Checks if a cfg attribute exists
+bool cfg_has(cfg_t *cfg, const char *key);
+
+// Retrieves a cfg attribute as a null-terminated string
+//
+// If the attribute does not exist, returns the string passed as def
+const char *cfg_get(cfg_t *cfg, const char *key, const char *def);
+
+// Retrieves a cfg attribute parsed as an int
+//
+// If the attribute does not exist or can't be parsed, returns the
+// integer passed as def
+ssize_t cfg_geti(cfg_t *cfg, const char *name, ssize_t def);
+
+// Retrieves a cfg attribute parsed as an unsigned int
+//
+// If the attribute does not exist or can't be parsed, returns the
+// integer passed as def
+size_t cfg_getu(cfg_t *cfg, const char *name, size_t def);
+
+#endif
