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-rw-r--r--notes.c317
1 files changed, 248 insertions, 69 deletions
diff --git a/notes.c b/notes.c
index a5d888d772..210c4b2263 100644
--- a/notes.c
+++ b/notes.c
@@ -6,109 +6,288 @@
#include "strbuf.h"
#include "tree-walk.h"
-struct entry {
- unsigned char commit_sha1[20];
- unsigned char notes_sha1[20];
+/*
+ * Use a non-balancing simple 16-tree structure with struct int_node as
+ * internal nodes, and struct leaf_node as leaf nodes. Each int_node has a
+ * 16-array of pointers to its children.
+ * The bottom 2 bits of each pointer is used to identify the pointer type
+ * - ptr & 3 == 0 - NULL pointer, assert(ptr == NULL)
+ * - ptr & 3 == 1 - pointer to next internal node - cast to struct int_node *
+ * - ptr & 3 == 2 - pointer to note entry - cast to struct leaf_node *
+ * - ptr & 3 == 3 - pointer to subtree entry - cast to struct leaf_node *
+ *
+ * The root node is a statically allocated struct int_node.
+ */
+struct int_node {
+ void *a[16];
};
-struct hash_map {
- struct entry *entries;
- off_t count, size;
+/*
+ * Leaf nodes come in two variants, note entries and subtree entries,
+ * distinguished by the LSb of the leaf node pointer (see above).
+ * As a note entry, the key is the SHA1 of the referenced commit, and the
+ * value is the SHA1 of the note object.
+ * As a subtree entry, the key is the prefix SHA1 (w/trailing NULs) of the
+ * referenced commit, using the last byte of the key to store the length of
+ * the prefix. The value is the SHA1 of the tree object containing the notes
+ * subtree.
+ */
+struct leaf_node {
+ unsigned char key_sha1[20];
+ unsigned char val_sha1[20];
};
-static int initialized;
-static struct hash_map hash_map;
+#define PTR_TYPE_NULL 0
+#define PTR_TYPE_INTERNAL 1
+#define PTR_TYPE_NOTE 2
+#define PTR_TYPE_SUBTREE 3
-static int hash_index(struct hash_map *map, const unsigned char *sha1)
-{
- int i = ((*(unsigned int *)sha1) % map->size);
+#define GET_PTR_TYPE(ptr) ((uintptr_t) (ptr) & 3)
+#define CLR_PTR_TYPE(ptr) ((void *) ((uintptr_t) (ptr) & ~3))
+#define SET_PTR_TYPE(ptr, type) ((void *) ((uintptr_t) (ptr) | (type)))
- for (;;) {
- unsigned char *current = map->entries[i].commit_sha1;
+#define GET_NIBBLE(n, sha1) (((sha1[n >> 1]) >> ((~n & 0x01) << 2)) & 0x0f)
- if (!hashcmp(sha1, current))
- return i;
+#define SUBTREE_SHA1_PREFIXCMP(key_sha1, subtree_sha1) \
+ (memcmp(key_sha1, subtree_sha1, subtree_sha1[19]))
- if (is_null_sha1(current))
- return -1 - i;
+static struct int_node root_node;
- if (++i == map->size)
- i = 0;
+static int initialized;
+
+static void load_subtree(struct leaf_node *subtree, struct int_node *node,
+ unsigned int n);
+
+/*
+ * To find a leaf_node:
+ * 1. Start at the root node, with n = 0
+ * 2. Use the nth nibble of the key as an index into a:
+ * - If a[n] is an int_node, recurse into that node and increment n
+ * - If a leaf_node with matching key, return leaf_node (assert note entry)
+ * - If a matching subtree entry, unpack that subtree entry (and remove it);
+ * restart search at the current level.
+ * - Otherwise, we end up at a NULL pointer, or a non-matching leaf_node.
+ * Backtrack out of the recursion, one level at a time and check a[0]:
+ * - If a[0] at the current level is a matching subtree entry, unpack that
+ * subtree entry (and remove it); restart search at the current level.
+ */
+static struct leaf_node *note_tree_find(struct int_node *tree, unsigned char n,
+ const unsigned char *key_sha1)
+{
+ struct leaf_node *l;
+ unsigned char i = GET_NIBBLE(n, key_sha1);
+ void *p = tree->a[i];
+
+ switch(GET_PTR_TYPE(p)) {
+ case PTR_TYPE_INTERNAL:
+ l = note_tree_find(CLR_PTR_TYPE(p), n + 1, key_sha1);
+ if (l)
+ return l;
+ break;
+ case PTR_TYPE_NOTE:
+ l = (struct leaf_node *) CLR_PTR_TYPE(p);
+ if (!hashcmp(key_sha1, l->key_sha1))
+ return l; /* return note object matching given key */
+ break;
+ case PTR_TYPE_SUBTREE:
+ l = (struct leaf_node *) CLR_PTR_TYPE(p);
+ if (!SUBTREE_SHA1_PREFIXCMP(key_sha1, l->key_sha1)) {
+ /* unpack tree and resume search */
+ tree->a[i] = NULL;
+ load_subtree(l, tree, n);
+ free(l);
+ return note_tree_find(tree, n, key_sha1);
+ }
+ break;
+ case PTR_TYPE_NULL:
+ default:
+ assert(!p);
+ break;
}
+
+ /*
+ * Did not find key at this (or any lower) level.
+ * Check if there's a matching subtree entry in tree->a[0].
+ * If so, unpack tree and resume search.
+ */
+ p = tree->a[0];
+ if (GET_PTR_TYPE(p) != PTR_TYPE_SUBTREE)
+ return NULL;
+ l = (struct leaf_node *) CLR_PTR_TYPE(p);
+ if (!SUBTREE_SHA1_PREFIXCMP(key_sha1, l->key_sha1)) {
+ /* unpack tree and resume search */
+ tree->a[0] = NULL;
+ load_subtree(l, tree, n);
+ free(l);
+ return note_tree_find(tree, n, key_sha1);
+ }
+ return NULL;
}
-static void add_entry(const unsigned char *commit_sha1,
- const unsigned char *notes_sha1)
+/*
+ * To insert a leaf_node:
+ * 1. Start at the root node, with n = 0
+ * 2. Use the nth nibble of the key as an index into a:
+ * - If a[n] is NULL, store the tweaked pointer directly into a[n]
+ * - If a[n] is an int_node, recurse into that node and increment n
+ * - If a[n] is a leaf_node:
+ * 1. Check if they're equal, and handle that (abort? overwrite?)
+ * 2. Create a new int_node, and store both leaf_nodes there
+ * 3. Store the new int_node into a[n].
+ */
+static int note_tree_insert(struct int_node *tree, unsigned char n,
+ const struct leaf_node *entry, unsigned char type)
{
- int index;
-
- if (hash_map.count + 1 > hash_map.size >> 1) {
- int i, old_size = hash_map.size;
- struct entry *old = hash_map.entries;
-
- hash_map.size = old_size ? old_size << 1 : 64;
- hash_map.entries = (struct entry *)
- xcalloc(sizeof(struct entry), hash_map.size);
-
- for (i = 0; i < old_size; i++)
- if (!is_null_sha1(old[i].commit_sha1)) {
- index = -1 - hash_index(&hash_map,
- old[i].commit_sha1);
- memcpy(hash_map.entries + index, old + i,
- sizeof(struct entry));
- }
- free(old);
+ struct int_node *new_node;
+ const struct leaf_node *l;
+ int ret;
+ unsigned char i = GET_NIBBLE(n, entry->key_sha1);
+ void *p = tree->a[i];
+ assert(GET_PTR_TYPE(entry) == PTR_TYPE_NULL);
+ switch(GET_PTR_TYPE(p)) {
+ case PTR_TYPE_NULL:
+ assert(!p);
+ tree->a[i] = SET_PTR_TYPE(entry, type);
+ return 0;
+ case PTR_TYPE_INTERNAL:
+ return note_tree_insert(CLR_PTR_TYPE(p), n + 1, entry, type);
+ default:
+ assert(GET_PTR_TYPE(p) == PTR_TYPE_NOTE ||
+ GET_PTR_TYPE(p) == PTR_TYPE_SUBTREE);
+ l = (const struct leaf_node *) CLR_PTR_TYPE(p);
+ if (!hashcmp(entry->key_sha1, l->key_sha1))
+ return -1; /* abort insert on matching key */
+ new_node = (struct int_node *)
+ xcalloc(sizeof(struct int_node), 1);
+ ret = note_tree_insert(new_node, n + 1,
+ CLR_PTR_TYPE(p), GET_PTR_TYPE(p));
+ if (ret) {
+ free(new_node);
+ return -1;
+ }
+ tree->a[i] = SET_PTR_TYPE(new_node, PTR_TYPE_INTERNAL);
+ return note_tree_insert(new_node, n + 1, entry, type);
}
+}
- index = hash_index(&hash_map, commit_sha1);
- if (index < 0) {
- index = -1 - index;
- hash_map.count++;
+/* Free the entire notes data contained in the given tree */
+static void note_tree_free(struct int_node *tree)
+{
+ unsigned int i;
+ for (i = 0; i < 16; i++) {
+ void *p = tree->a[i];
+ switch(GET_PTR_TYPE(p)) {
+ case PTR_TYPE_INTERNAL:
+ note_tree_free(CLR_PTR_TYPE(p));
+ /* fall through */
+ case PTR_TYPE_NOTE:
+ case PTR_TYPE_SUBTREE:
+ free(CLR_PTR_TYPE(p));
+ }
}
+}
- hashcpy(hash_map.entries[index].commit_sha1, commit_sha1);
- hashcpy(hash_map.entries[index].notes_sha1, notes_sha1);
+/*
+ * Convert a partial SHA1 hex string to the corresponding partial SHA1 value.
+ * - hex - Partial SHA1 segment in ASCII hex format
+ * - hex_len - Length of above segment. Must be multiple of 2 between 0 and 40
+ * - sha1 - Partial SHA1 value is written here
+ * - sha1_len - Max #bytes to store in sha1, Must be >= hex_len / 2, and < 20
+ * Returns -1 on error (invalid arguments or invalid SHA1 (not in hex format).
+ * Otherwise, returns number of bytes written to sha1 (i.e. hex_len / 2).
+ * Pads sha1 with NULs up to sha1_len (not included in returned length).
+ */
+static int get_sha1_hex_segment(const char *hex, unsigned int hex_len,
+ unsigned char *sha1, unsigned int sha1_len)
+{
+ unsigned int i, len = hex_len >> 1;
+ if (hex_len % 2 != 0 || len > sha1_len)
+ return -1;
+ for (i = 0; i < len; i++) {
+ unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
+ if (val & ~0xff)
+ return -1;
+ *sha1++ = val;
+ hex += 2;
+ }
+ for (; i < sha1_len; i++)
+ *sha1++ = 0;
+ return len;
}
-static void initialize_hash_map(const char *notes_ref_name)
+static void load_subtree(struct leaf_node *subtree, struct int_node *node,
+ unsigned int n)
{
- unsigned char sha1[20], commit_sha1[20];
- unsigned mode;
+ unsigned char commit_sha1[20];
+ unsigned int prefix_len;
+ int status;
+ void *buf;
struct tree_desc desc;
struct name_entry entry;
- void *buf;
+
+ buf = fill_tree_descriptor(&desc, subtree->val_sha1);
+ if (!buf)
+ die("Could not read %s for notes-index",
+ sha1_to_hex(subtree->val_sha1));
+
+ prefix_len = subtree->key_sha1[19];
+ assert(prefix_len * 2 >= n);
+ memcpy(commit_sha1, subtree->key_sha1, prefix_len);
+ while (tree_entry(&desc, &entry)) {
+ int len = get_sha1_hex_segment(entry.path, strlen(entry.path),
+ commit_sha1 + prefix_len, 20 - prefix_len);
+ if (len < 0)
+ continue; /* entry.path is not a SHA1 sum. Skip */
+ len += prefix_len;
+
+ /*
+ * If commit SHA1 is complete (len == 20), assume note object
+ * If commit SHA1 is incomplete (len < 20), assume note subtree
+ */
+ if (len <= 20) {
+ unsigned char type = PTR_TYPE_NOTE;
+ struct leaf_node *l = (struct leaf_node *)
+ xcalloc(sizeof(struct leaf_node), 1);
+ hashcpy(l->key_sha1, commit_sha1);
+ hashcpy(l->val_sha1, entry.sha1);
+ if (len < 20) {
+ l->key_sha1[19] = (unsigned char) len;
+ type = PTR_TYPE_SUBTREE;
+ }
+ status = note_tree_insert(node, n, l, type);
+ assert(!status);
+ }
+ }
+ free(buf);
+}
+
+static void initialize_notes(const char *notes_ref_name)
+{
+ unsigned char sha1[20], commit_sha1[20];
+ unsigned mode;
+ struct leaf_node root_tree;
if (!notes_ref_name || read_ref(notes_ref_name, commit_sha1) ||
get_tree_entry(commit_sha1, "", sha1, &mode))
return;
- buf = fill_tree_descriptor(&desc, sha1);
- if (!buf)
- die("Could not read %s for notes-index", sha1_to_hex(sha1));
-
- while (tree_entry(&desc, &entry))
- if (!get_sha1(entry.path, commit_sha1))
- add_entry(commit_sha1, entry.sha1);
- free(buf);
+ hashclr(root_tree.key_sha1);
+ hashcpy(root_tree.val_sha1, sha1);
+ load_subtree(&root_tree, &root_node, 0);
}
static unsigned char *lookup_notes(const unsigned char *commit_sha1)
{
- int index;
-
- if (!hash_map.size)
- return NULL;
-
- index = hash_index(&hash_map, commit_sha1);
- if (index < 0)
- return NULL;
- return hash_map.entries[index].notes_sha1;
+ struct leaf_node *found = note_tree_find(&root_node, 0, commit_sha1);
+ if (found)
+ return found->val_sha1;
+ return NULL;
}
void free_notes(void)
{
- free(hash_map.entries);
- memset(&hash_map, 0, sizeof(struct hash_map));
+ note_tree_free(&root_node);
+ memset(&root_node, 0, sizeof(struct int_node));
initialized = 0;
}
@@ -127,7 +306,7 @@ void get_commit_notes(const struct commit *commit, struct strbuf *sb,
notes_ref_name = getenv(GIT_NOTES_REF_ENVIRONMENT);
else if (!notes_ref_name)
notes_ref_name = GIT_NOTES_DEFAULT_REF;
- initialize_hash_map(notes_ref_name);
+ initialize_notes(notes_ref_name);
initialized = 1;
}