esp-idf/components/log/log.c

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2021-04-12 02:02:59 -04:00
/*
* SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
/*
* Log library implementation notes.
*
* Log library stores all tags provided to esp_log_level_set as a linked
* list. See uncached_tag_entry_t structure.
*
* To avoid looking up log level for given tag each time message is
* printed, this library caches pointers to tags. Because the suggested
* way of creating tags uses one 'TAG' constant per file, this caching
* should be effective. Cache is a binary min-heap of cached_tag_entry_t
* items, ordering is done on 'generation' member. In this context,
* generation is an integer which is incremented each time an operation
* with cache is performed. When cache is full, new item is inserted in
* place of an oldest item (that is, with smallest 'generation' value).
* After that, bubble-down operation is performed to fix ordering in the
* min-heap.
*
* The potential problem with wrap-around of cache generation counter is
* ignored for now. This will happen if someone happens to output more
* than 4 billion log entries, at which point wrap-around will not be
* the biggest problem.
*
*/
#include <stdbool.h>
#include <stdarg.h>
#include <stddef.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include "esp_log.h"
#include "esp_log_private.h"
#ifndef NDEBUG
// Enable built-in checks in queue.h in debug builds
#define INVARIANTS
// Enable consistency checks and cache statistics in this file.
#define LOG_BUILTIN_CHECKS
#endif
#include "sys/queue.h"
// Number of tags to be cached. Must be 2**n - 1, n >= 2.
#define TAG_CACHE_SIZE 31
typedef struct {
const char *tag;
uint32_t level : 3;
uint32_t generation : 29;
} cached_tag_entry_t;
typedef struct uncached_tag_entry_ {
SLIST_ENTRY(uncached_tag_entry_) entries;
uint8_t level; // esp_log_level_t as uint8_t
char tag[0]; // beginning of a zero-terminated string
} uncached_tag_entry_t;
esp_log_level_t esp_log_default_level = CONFIG_LOG_DEFAULT_LEVEL;
static SLIST_HEAD(log_tags_head, uncached_tag_entry_) s_log_tags = SLIST_HEAD_INITIALIZER(s_log_tags);
static cached_tag_entry_t s_log_cache[TAG_CACHE_SIZE];
static uint32_t s_log_cache_max_generation = 0;
static uint32_t s_log_cache_entry_count = 0;
static vprintf_like_t s_log_print_func = &vprintf;
#ifdef LOG_BUILTIN_CHECKS
static uint32_t s_log_cache_misses = 0;
#endif
static inline bool get_cached_log_level(const char *tag, esp_log_level_t *level);
static inline bool get_uncached_log_level(const char *tag, esp_log_level_t *level);
static inline void add_to_cache(const char *tag, esp_log_level_t level);
static void heap_bubble_down(int index);
static inline void heap_swap(int i, int j);
static inline bool should_output(esp_log_level_t level_for_message, esp_log_level_t level_for_tag);
static inline void clear_log_level_list(void);
vprintf_like_t esp_log_set_vprintf(vprintf_like_t func)
{
esp_log_impl_lock();
vprintf_like_t orig_func = s_log_print_func;
s_log_print_func = func;
esp_log_impl_unlock();
return orig_func;
}
void esp_log_level_set(const char *tag, esp_log_level_t level)
{
esp_log_impl_lock();
// for wildcard tag, remove all linked list items and clear the cache
if (strcmp(tag, "*") == 0) {
esp_log_default_level = level;
clear_log_level_list();
esp_log_impl_unlock();
return;
}
// search for existing tag
uncached_tag_entry_t *it = NULL;
SLIST_FOREACH(it, &s_log_tags, entries) {
if (strcmp(it->tag, tag) == 0) {
// one tag in the linked list matched, update the level
it->level = level;
// quit with it != NULL
break;
}
}
// no existing tag, append new one
if (it == NULL) {
// allocate new linked list entry and append it to the head of the list
size_t tag_len = strlen(tag) + 1;
size_t entry_size = offsetof(uncached_tag_entry_t, tag) + tag_len;
uncached_tag_entry_t *new_entry = (uncached_tag_entry_t *) malloc(entry_size);
if (!new_entry) {
esp_log_impl_unlock();
return;
}
new_entry->level = (uint8_t) level;
memcpy(new_entry->tag, tag, tag_len); // we know the size and strncpy would trigger a compiler warning here
SLIST_INSERT_HEAD(&s_log_tags, new_entry, entries);
}
// search in the cache and update the entry it if exists
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for (uint32_t i = 0; i < s_log_cache_entry_count; ++i) {
#ifdef LOG_BUILTIN_CHECKS
assert(i == 0 || s_log_cache[(i - 1) / 2].generation < s_log_cache[i].generation);
#endif
if (strcmp(s_log_cache[i].tag, tag) == 0) {
s_log_cache[i].level = level;
break;
}
}
esp_log_impl_unlock();
}
void clear_log_level_list(void)
{
uncached_tag_entry_t *it;
while ((it = SLIST_FIRST(&s_log_tags)) != NULL) {
SLIST_REMOVE_HEAD(&s_log_tags, entries);
free(it);
}
s_log_cache_entry_count = 0;
s_log_cache_max_generation = 0;
#ifdef LOG_BUILTIN_CHECKS
s_log_cache_misses = 0;
#endif
}
void esp_log_writev(esp_log_level_t level,
const char *tag,
const char *format,
va_list args)
{
if (!esp_log_impl_lock_timeout()) {
return;
}
esp_log_level_t level_for_tag;
// Look for the tag in cache first, then in the linked list of all tags
if (!get_cached_log_level(tag, &level_for_tag)) {
if (!get_uncached_log_level(tag, &level_for_tag)) {
level_for_tag = esp_log_default_level;
}
add_to_cache(tag, level_for_tag);
#ifdef LOG_BUILTIN_CHECKS
++s_log_cache_misses;
#endif
}
esp_log_impl_unlock();
if (!should_output(level, level_for_tag)) {
return;
}
(*s_log_print_func)(format, args);
}
void esp_log_write(esp_log_level_t level,
const char *tag,
const char *format, ...)
{
va_list list;
va_start(list, format);
esp_log_writev(level, tag, format, list);
va_end(list);
}
static inline bool get_cached_log_level(const char *tag, esp_log_level_t *level)
{
// Look for `tag` in cache
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uint32_t i;
for (i = 0; i < s_log_cache_entry_count; ++i) {
#ifdef LOG_BUILTIN_CHECKS
assert(i == 0 || s_log_cache[(i - 1) / 2].generation < s_log_cache[i].generation);
#endif
if (s_log_cache[i].tag == tag) {
break;
}
}
if (i == s_log_cache_entry_count) { // Not found in cache
return false;
}
// Return level from cache
*level = (esp_log_level_t) s_log_cache[i].level;
// If cache has been filled, start taking ordering into account
// (other options are: dynamically resize cache, add "dummy" entries
// to the cache; this option was chosen because code is much simpler,
// and the unfair behavior of cache will show it self at most once, when
// it has just been filled)
if (s_log_cache_entry_count == TAG_CACHE_SIZE) {
// Update item generation
s_log_cache[i].generation = s_log_cache_max_generation++;
// Restore heap ordering
heap_bubble_down(i);
}
return true;
}
static inline void add_to_cache(const char *tag, esp_log_level_t level)
{
uint32_t generation = s_log_cache_max_generation++;
// First consider the case when cache is not filled yet.
// In this case, just add new entry at the end.
// This happens to satisfy binary min-heap ordering.
if (s_log_cache_entry_count < TAG_CACHE_SIZE) {
s_log_cache[s_log_cache_entry_count] = (cached_tag_entry_t) {
.generation = generation,
.level = level,
.tag = tag
};
++s_log_cache_entry_count;
return;
}
// Cache is full, so we replace the oldest entry (which is at index 0
// because this is a min-heap) with the new one, and do bubble-down
// operation to restore min-heap ordering.
s_log_cache[0] = (cached_tag_entry_t) {
.tag = tag,
.level = level,
.generation = generation
};
heap_bubble_down(0);
}
static inline bool get_uncached_log_level(const char *tag, esp_log_level_t *level)
{
// Walk the linked list of all tags and see if given tag is present in the list.
// This is slow because tags are compared as strings.
uncached_tag_entry_t *it;
SLIST_FOREACH(it, &s_log_tags, entries) {
if (strcmp(tag, it->tag) == 0) {
*level = it->level;
return true;
}
}
return false;
}
static inline bool should_output(esp_log_level_t level_for_message, esp_log_level_t level_for_tag)
{
return level_for_message <= level_for_tag;
}
static void heap_bubble_down(int index)
{
while (index < TAG_CACHE_SIZE / 2) {
int left_index = index * 2 + 1;
int right_index = left_index + 1;
int next = (s_log_cache[left_index].generation < s_log_cache[right_index].generation) ? left_index : right_index;
heap_swap(index, next);
index = next;
}
}
static inline void heap_swap(int i, int j)
{
cached_tag_entry_t tmp = s_log_cache[i];
s_log_cache[i] = s_log_cache[j];
s_log_cache[j] = tmp;
}