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tag: v1.7.0.7
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#include "cache.h"
#include "commit.h"
#include "notes.h"
#include "refs.h"
#include "utf8.h"
#include "strbuf.h"
#include "tree-walk.h"

/*
* 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];
};

/*
* 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];
};

#define PTR_TYPE_NULL 0
#define PTR_TYPE_INTERNAL 1
#define PTR_TYPE_NOTE 2
#define PTR_TYPE_SUBTREE 3

#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)))

#define GET_NIBBLE(n, sha1) (((sha1[n >> 1]) >> ((~n & 0x01) << 2)) & 0x0f)

#define SUBTREE_SHA1_PREFIXCMP(key_sha1, subtree_sha1) \
(memcmp(key_sha1, subtree_sha1, subtree_sha1[19]))

static struct int_node root_node;

static int initialized;

static void load_subtree(struct leaf_node *subtree, struct int_node *node,
unsigned int n);

/*
* Search the tree until the appropriate location for the given key is found:
* 1. Start at the root node, with n = 0
* 2. 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.
* 3. Use the nth nibble of the key as an index into a:
* - If a[n] is an int_node, recurse from #2 into that node and increment n
* - If a matching subtree entry, unpack that subtree entry (and remove it);
* restart search at the current level.
* - Otherwise, we have found one of the following:
* - a subtree entry which does not match the key
* - a note entry which may or may not match the key
* - an unused leaf node (NULL)
* In any case, set *tree and *n, and return pointer to the tree location.
*/
static void **note_tree_search(struct int_node **tree,
unsigned char *n, const unsigned char *key_sha1)
{
struct leaf_node *l;
unsigned char i;
void *p = (*tree)->a[0];

if (GET_PTR_TYPE(p) == 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[0] = NULL;
load_subtree(l, *tree, *n);
free(l);
return note_tree_search(tree, n, key_sha1);
}
}

i = GET_NIBBLE(*n, key_sha1);
p = (*tree)->a[i];
switch(GET_PTR_TYPE(p)) {
case PTR_TYPE_INTERNAL:
*tree = CLR_PTR_TYPE(p);
(*n)++;
return note_tree_search(tree, n, key_sha1);
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_search(tree, n, key_sha1);
}
/* fall through */
default:
return &((*tree)->a[i]);
}
}

/*
* To find a leaf_node:
* Search to the tree location appropriate for the given key:
* If a note entry with matching key, return the note entry, else return NULL.
*/
static struct leaf_node *note_tree_find(struct int_node *tree, unsigned char n,
const unsigned char *key_sha1)
{
void **p = note_tree_search(&tree, &n, key_sha1);
if (GET_PTR_TYPE(*p) == PTR_TYPE_NOTE) {
struct leaf_node *l = (struct leaf_node *) CLR_PTR_TYPE(*p);
if (!hashcmp(key_sha1, l->key_sha1))
return l;
}
return NULL;
}

/* Create a new blob object by concatenating the two given blob objects */
static int concatenate_notes(unsigned char *cur_sha1,
const unsigned char *new_sha1)
{
char *cur_msg, *new_msg, *buf;
unsigned long cur_len, new_len, buf_len;
enum object_type cur_type, new_type;
int ret;

/* read in both note blob objects */
new_msg = read_sha1_file(new_sha1, &new_type, &new_len);
if (!new_msg || !new_len || new_type != OBJ_BLOB) {
free(new_msg);
return 0;
}
cur_msg = read_sha1_file(cur_sha1, &cur_type, &cur_len);
if (!cur_msg || !cur_len || cur_type != OBJ_BLOB) {
free(cur_msg);
free(new_msg);
hashcpy(cur_sha1, new_sha1);
return 0;
}

/* we will separate the notes by a newline anyway */
if (cur_msg[cur_len - 1] == '\n')
cur_len--;

/* concatenate cur_msg and new_msg into buf */
buf_len = cur_len + 1 + new_len;
buf = (char *) xmalloc(buf_len);
memcpy(buf, cur_msg, cur_len);
buf[cur_len] = '\n';
memcpy(buf + cur_len + 1, new_msg, new_len);

free(cur_msg);
free(new_msg);

/* create a new blob object from buf */
ret = write_sha1_file(buf, buf_len, "blob", cur_sha1);
free(buf);
return ret;
}

/*
* To insert a leaf_node:
* Search to the tree location appropriate for the given leaf_node's key:
* - If location is unused (NULL), store the tweaked pointer directly there
* - If location holds a note entry that matches the note-to-be-inserted, then
* concatenate the two notes.
* - If location holds a note entry that matches the subtree-to-be-inserted,
* then unpack the subtree-to-be-inserted into the location.
* - If location holds a matching subtree entry, unpack the subtree at that
* location, and restart the insert operation from that level.
* - Else, create a new int_node, holding both the node-at-location and the
* node-to-be-inserted, and store the new int_node into the location.
*/
static void note_tree_insert(struct int_node *tree, unsigned char n,
struct leaf_node *entry, unsigned char type)
{
struct int_node *new_node;
struct leaf_node *l;
void **p = note_tree_search(&tree, &n, entry->key_sha1);

assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
l = (struct leaf_node *) CLR_PTR_TYPE(*p);
switch(GET_PTR_TYPE(*p)) {
case PTR_TYPE_NULL:
assert(!*p);
*p = SET_PTR_TYPE(entry, type);
return;
case PTR_TYPE_NOTE:
switch (type) {
case PTR_TYPE_NOTE:
if (!hashcmp(l->key_sha1, entry->key_sha1)) {
/* skip concatenation if l == entry */
if (!hashcmp(l->val_sha1, entry->val_sha1))
return;

if (concatenate_notes(l->val_sha1,
entry->val_sha1))
die("failed to concatenate note %s "
"into note %s for commit %s",
sha1_to_hex(entry->val_sha1),
sha1_to_hex(l->val_sha1),
sha1_to_hex(l->key_sha1));
free(entry);
return;
}
break;
case PTR_TYPE_SUBTREE:
if (!SUBTREE_SHA1_PREFIXCMP(l->key_sha1,
entry->key_sha1)) {
/* unpack 'entry' */
load_subtree(entry, tree, n);
free(entry);
return;
}
break;
}
break;
case PTR_TYPE_SUBTREE:
if (!SUBTREE_SHA1_PREFIXCMP(entry->key_sha1, l->key_sha1)) {
/* unpack 'l' and restart insert */
*p = NULL;
load_subtree(l, tree, n);
free(l);
note_tree_insert(tree, n, entry, type);
return;
}
break;
}

/* non-matching leaf_node */
assert(GET_PTR_TYPE(*p) == PTR_TYPE_NOTE ||
GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
new_node = (struct int_node *) xcalloc(sizeof(struct int_node), 1);
note_tree_insert(new_node, n + 1, l, GET_PTR_TYPE(*p));
*p = SET_PTR_TYPE(new_node, PTR_TYPE_INTERNAL);
note_tree_insert(new_node, n + 1, entry, type);
}

/* 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));
}
}
}

/*
* 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 load_subtree(struct leaf_node *subtree, struct int_node *node,
unsigned int n)
{
unsigned char commit_sha1[20];
unsigned int prefix_len;
void *buf;
struct tree_desc desc;
struct name_entry entry;

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) {
if (!S_ISDIR(entry.mode))
continue; /* entry cannot be subtree */
l->key_sha1[19] = (unsigned char) len;
type = PTR_TYPE_SUBTREE;
}
note_tree_insert(node, n, l, type);
}
}
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;

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)
{
struct leaf_node *found = note_tree_find(&root_node, 0, commit_sha1);
if (found)
return found->val_sha1;
return NULL;
}

void free_notes(void)
{
note_tree_free(&root_node);
memset(&root_node, 0, sizeof(struct int_node));
initialized = 0;
}

void get_commit_notes(const struct commit *commit, struct strbuf *sb,
const char *output_encoding, int flags)
{
static const char utf8[] = "utf-8";
unsigned char *sha1;
char *msg, *msg_p;
unsigned long linelen, msglen;
enum object_type type;

if (!initialized) {
const char *env = getenv(GIT_NOTES_REF_ENVIRONMENT);
if (env)
notes_ref_name = getenv(GIT_NOTES_REF_ENVIRONMENT);
else if (!notes_ref_name)
notes_ref_name = GIT_NOTES_DEFAULT_REF;
initialize_notes(notes_ref_name);
initialized = 1;
}

sha1 = lookup_notes(commit->object.sha1);
if (!sha1)
return;

if (!(msg = read_sha1_file(sha1, &type, &msglen)) || !msglen ||
type != OBJ_BLOB) {
free(msg);
return;
}

if (output_encoding && *output_encoding &&
strcmp(utf8, output_encoding)) {
char *reencoded = reencode_string(msg, output_encoding, utf8);
if (reencoded) {
free(msg);
msg = reencoded;
msglen = strlen(msg);
}
}

/* we will end the annotation by a newline anyway */
if (msglen && msg[msglen - 1] == '\n')
msglen--;

if (flags & NOTES_SHOW_HEADER)
strbuf_addstr(sb, "\nNotes:\n");

for (msg_p = msg; msg_p < msg + msglen; msg_p += linelen + 1) {
linelen = strchrnul(msg_p, '\n') - msg_p;

if (flags & NOTES_INDENT)
strbuf_addstr(sb, " ");
strbuf_add(sb, msg_p, linelen);
strbuf_addch(sb, '\n');
}

free(msg);
}
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