perror(PNAME ": mmap");
return 1;
}
+ if (!trie_check_magic(mappedfile)) {
+ fprintf(stderr, "%s: %s: magic numbers did not match\n"
+ "%s: check that the index was built by this version of agedu on this platform\n", PNAME, filename, PNAME);
+ return 1;
+ }
pathsep = trie_pathsep(mappedfile);
/*
}
return 1;
}
+ if (!trie_check_magic(mappedfile)) {
+ fprintf(stderr, "%s: %s: magic numbers did not match\n"
+ "%s: check that the index was built by this version of agedu on this platform\n", PNAME, filename, PNAME);
+ if (!querydir) {
+ printf("Status: 500\nContent-type: text/html\n\n"
+ "<html><head>"
+ "<title>500 Internal Server Error</title>"
+ "</head><body>"
+ "<h1>500 Internal Server Error</h1>"
+ "<p><code>agedu</code> suffered an internal error."
+ "</body></html>\n");
+ return 0;
+ }
+ return 1;
+ }
pathsep = trie_pathsep(mappedfile);
maxpathlen = trie_maxpathlen(mappedfile);
perror(PNAME ": mmap");
return 1;
}
+ if (!trie_check_magic(mappedfile)) {
+ fprintf(stderr, "%s: %s: magic numbers did not match\n"
+ "%s: check that the index was built by this version of agedu on this platform\n", PNAME, filename, PNAME);
+ return 1;
+ }
pathsep = trie_pathsep(mappedfile);
maxpathlen = trie_maxpathlen(mappedfile);
perror(PNAME ": mmap");
return 1;
}
+ if (!trie_check_magic(mappedfile)) {
+ fprintf(stderr, "%s: %s: magic numbers did not match\n"
+ "%s: check that the index was built by this version of agedu on this platform\n", PNAME, filename, PNAME);
+ return 1;
+ }
pathsep = trie_pathsep(mappedfile);
dcfg.address = httpserveraddr;
char string[];
};
+static const char magic_ident_string[16] = "agedu index file";
+struct trie_magic {
+ /*
+ * 'Magic numbers' to go at the start of an agedu index file.
+ * These are checked (using trie_check_magic) by every agedu mode
+ * which reads a pre-existing index.
+ *
+ * As well as identifying an agedu file from any other kind of
+ * file, this magic-number structure is also intended to detect
+ * agedu files which were written on the wrong platform and hence
+ * whose structure layouts are incompatible. To make that as
+ * reliable as possible, I design the structure of magic numbers
+ * as follows: it contains one of each integer type I might use,
+ * each containing a different magic number, and each followed by
+ * a char to indicate where it ends in the file. One byte is set
+ * to the length of the magic-number structure itself, which means
+ * that no two structures of different lengths can possibly
+ * compare equal even if by some chance they match up to the
+ * length of the shorter one. Finally, the whole magic number
+ * structure is memset to another random byte value before
+ * initialising any of these fields, so that padding in between
+ * can be readily identified.
+ */
+ char ident[16]; /* human-readable string */
+
+ unsigned char magic_len;
+
+ unsigned long long longlong_magic;
+ unsigned char postlonglong_char_magic;
+
+ off_t offset_magic;
+ unsigned char postoffset_char_magic;
+
+ size_t size_magic;
+ unsigned char postsize_char_magic;
+
+ void *null_pointer;
+ unsigned char postptr_char_magic;
+
+ unsigned long long_magic;
+ unsigned char postlong_char_magic;
+
+ unsigned short short_magic;
+ unsigned char postshort_char_magic;
+};
+
struct trie_header {
- unsigned long magic;
+ struct trie_magic magic;
off_t root, indexroot;
int count;
size_t maxpathlen;
char string[1];
} str;
};
-#define TRIE_MAGIC 0x75646761UL
#define TRIE_ALIGN alignof(union trie_node)
+static void setup_magic(struct trie_magic *th)
+{
+ /*
+ * Magic values are chosen so that every byte value used is
+ * distinct (so that we can't fail to spot endianness issues), and
+ * we cast 64 bits of data into each integer type just in case
+ * the platform makes it longer than we expect it to be.
+ */
+
+ memset(th, 0xCDU, sizeof(*th));
+
+ th->magic_len = sizeof(*th);
+
+ memcpy(th->ident, magic_ident_string, 16);
+
+ th->longlong_magic = 0x5583F34D5D84F73CULL;
+ th->postlonglong_char_magic = 0xDDU;
+
+ th->offset_magic = (off_t)0xB39BF9AD56D48E0BULL;
+ th->postoffset_char_magic = 0x95U;
+
+ th->size_magic = (size_t)0x6EC752B0EEAEBAC1ULL;
+ th->postsize_char_magic = 0x77U;
+
+ th->null_pointer = NULL;
+ th->postptr_char_magic = 0x71U;
+
+ th->long_magic = (unsigned long)0xA81A5E1F44334716ULL;
+ th->postlong_char_magic = 0x99U;
+
+ th->short_magic = (unsigned short)0x0C8BD7984B68D9FCULL;
+ th->postshort_char_magic = 0x35U;
+}
+
/* ----------------------------------------------------------------------
* Trie-building functions.
*/
tb->switchsize = 0;
tb->maxpathlen = 0;
- th.magic = TRIE_MAGIC;
+ setup_magic(&th.magic);
th.root = th.count = 0;
th.indexroot = 0;
th.maxpathlen = 0;
{
struct trie_header th;
- th.magic = TRIE_MAGIC;
+ setup_magic(&th.magic);
th.root = triebuild_unwind(tb, 0, &th.count);
th.indexroot = 0;
th.maxpathlen = tb->maxpathlen;
#define NODE(t, off, type) \
((const struct type *)((const char *)(t) + (off)))
+int trie_check_magic(const void *t)
+{
+ const struct trie_header *hdr = NODE(t, 0, trie_header);
+ struct trie_magic magic;
+
+ setup_magic(&magic);
+ return !memcmp(&magic, &hdr->magic, sizeof(magic));
+}
+
size_t trie_maxpathlen(const void *t)
{
const struct trie_header *hdr = NODE(t, 0, trie_header);
~mdw / sgt / agedu / commitdiff