1Android liblog 2-------------- 3 4Public Functions and Macros 5--------------------------- 6 7 /* 8 * Please limit to 24 characters for runtime is loggable, 9 * 16 characters for persist is loggable, and logcat pretty 10 * alignment with limit of 7 characters. 11 */ 12 #define LOG_TAG "yourtag" 13 #include <log/log.h> 14 15 ALOG(android_priority, tag, format, ...) 16 IF_ALOG(android_priority, tag) 17 LOG_PRI(priority, tag, format, ...) 18 LOG_PRI_VA(priority, tag, format, args) 19 #define LOG_TAG NULL 20 ALOGV(format, ...) 21 SLOGV(format, ...) 22 RLOGV(format, ...) 23 ALOGV_IF(cond, format, ...) 24 SLOGV_IF(cond, format, ...) 25 RLOGV_IF(cond, format, ...) 26 IF_ALOGC() 27 ALOGD(format, ...) 28 SLOGD(format, ...) 29 RLOGD(format, ...) 30 ALOGD_IF(cond, format, ...) 31 SLOGD_IF(cond, format, ...) 32 RLOGD_IF(cond, format, ...) 33 IF_ALOGD() 34 ALOGI(format, ...) 35 SLOGI(format, ...) 36 RLOGI(format, ...) 37 ALOGI_IF(cond, format, ...) 38 SLOGI_IF(cond, format, ...) 39 RLOGI_IF(cond, format, ...) 40 IF_ALOGI() 41 ALOGW(format, ...) 42 SLOGW(format, ...) 43 RLOGW(format, ...) 44 ALOGW_IF(cond, format, ...) 45 SLOGW_IF(cond, format, ...) 46 RLOGW_IF(cond, format, ...) 47 IF_ALOGW() 48 ALOGE(format, ...) 49 SLOGE(format, ...) 50 RLOGE(format, ...) 51 ALOGE_IF(cond, format, ...) 52 SLOGE_IF(cond, format, ...) 53 RLOGE_IF(cond, format, ...) 54 IF_ALOGE() 55 LOG_FATAL(format, ...) 56 LOG_ALWAYS_FATAL(format, ...) 57 LOG_FATAL_IF(cond, format, ...) 58 LOG_ALWAYS_FATAL_IF(cond, format, ...) 59 ALOG_ASSERT(cond, format, ...) 60 LOG_EVENT_INT(tag, value) 61 LOG_EVENT_LONG(tag, value) 62 63 log_id_t android_logger_get_id(struct logger *logger) 64 int android_logger_clear(struct logger *logger) 65 int android_logger_get_log_size(struct logger *logger) 66 int android_logger_get_log_readable_size(struct logger *logger) 67 int android_logger_get_log_version(struct logger *logger) 68 69 struct logger_list *android_logger_list_alloc(int mode, unsigned int tail, pid_t pid) 70 struct logger *android_logger_open(struct logger_list *logger_list, log_id_t id) 71 struct logger_list *android_logger_list_open(log_id_t id, int mode, unsigned int tail, pid_t pid) 72 int android_logger_list_read(struct logger_list *logger_list, struct log_msg *log_msg) 73 void android_logger_list_free(struct logger_list *logger_list) 74 75 log_id_t android_name_to_log_id(const char *logName) 76 const char *android_log_id_to_name(log_id_t log_id) 77 78 android_log_context create_android_logger(uint32_t tag) 79 80 int android_log_write_list_begin(android_log_context ctx) 81 int android_log_write_list_end(android_log_context ctx) 82 83 int android_log_write_int32(android_log_context ctx, int32_t value) 84 int android_log_write_int64(android_log_context ctx, int64_t value) 85 int android_log_write_string8(android_log_context ctx, const char *value) 86 int android_log_write_string8_len(android_log_context ctx, const char *value, size_t maxlen) 87 int android_log_write_float32(android_log_context ctx, float value) 88 89 int android_log_write_list(android_log_context ctx, log_id_t id = LOG_ID_EVENTS) 90 91 android_log_context create_android_log_parser(const char *msg, size_t len) 92 android_log_list_element android_log_read_next(android_log_context ctx) 93 android_log_list_element android_log_peek_next(android_log_context ctx) 94 95 int android_log_destroy(android_log_context *ctx) 96 97Description 98----------- 99 100liblog represents an interface to the volatile Android Logging system for NDK (Native) applications 101and libraries. Interfaces for either writing or reading logs. The log buffers are divided up in 102Main, System, Radio and Events sub-logs. 103 104The logging interfaces are a series of macros, all of which can be overridden individually in order 105to control the verbosity of the application or library. `[ASR]LOG[VDIWE]` calls are used to log to 106BAsic, System or Radio sub-logs in either the Verbose, Debug, Info, Warning or Error priorities. 107`[ASR]LOG[VDIWE]_IF` calls are used to perform thus based on a condition being true. 108`IF_ALOG[VDIWE]` calls are true if the current `LOG_TAG` is enabled at the specified priority. 109`LOG_ALWAYS_FATAL` is used to `ALOG` a message, then kill the process. `LOG_FATAL` call is a 110variant of `LOG_ALWAYS_FATAL`, only enabled in engineering, and not release builds. `ALOG_ASSERT` 111is used to `ALOG` a message if the condition is false; the condition is part of the logged message. 112`LOG_EVENT_(INT|LONG)` is used to drop binary content into the Events sub-log. 113 114The log reading interfaces permit opening the logs either singly or multiply, retrieving a log entry 115at a time in time sorted order, optionally limited to a specific pid and tail of the log(s) and 116finally a call closing the logs. A single log can be opened with `android_logger_list_open()`; or 117multiple logs can be opened with `android_logger_list_alloc()`, calling in turn the 118`android_logger_open()` for each log id. Each entry can be retrieved with 119`android_logger_list_read()`. The log(s) can be closed with `android_logger_list_free()`. 120`ANDROID_LOG_NONBLOCK` mode will report when the log reading is done with an `EAGAIN` error return 121code, otherwise the `android_logger_list_read()` call will block for new entries. 122 123The `ANDROID_LOG_WRAP` mode flag to the `android_logger_list_alloc_time()` signals logd to quiesce 124the reader until the buffer is about to prune at the start time then proceed to dumping content. 125 126The `ANDROID_LOG_PSTORE` mode flag to the `android_logger_open()` is used to switch from the active 127logs to the persistent logs from before the last reboot. 128 129The value returned by `android_logger_open()` can be used as a parameter to the 130`android_logger_clear()` function to empty the sub-log. 131 132The value returned by `android_logger_open()` can be used as a parameter to the 133`android_logger_get_log_(size|readable_size|version)` to retrieve the sub-log maximum size, readable 134size and log buffer format protocol version respectively. `android_logger_get_id()` returns the id 135that was used when opening the sub-log. 136 137Errors 138------ 139 140If messages fail, a negative error code will be returned to the caller. 141 142The `-ENOTCONN` return code indicates that the logger daemon is stopped. 143 144The `-EBADF` return code indicates that the log access point can not be opened, or the log buffer id 145is out of range. 146 147For the `-EAGAIN` return code, this means that the logging message was temporarily backed-up either 148because of Denial Of Service (DOS) logging pressure from some chatty application or service in the 149Android system, or if too small of a value is set in /proc/sys/net/unix/max_dgram_qlen. To aid in 150diagnosing the occurence of this, a binary event from liblog will be sent to the log daemon once a 151new message can get through indicating how many messages were dropped as a result. Please take 152action to resolve the structural problems at the source. 153 154It is generally not advised for the caller to retry the `-EAGAIN` return code as this will only make 155the problem(s) worse and cause your application to temporarily drop to the logger daemon priority, 156BATCH scheduling policy and background task cgroup. If you require a group of messages to be passed 157atomically, merge them into one message with embedded newlines to the maximum length 158`LOGGER_ENTRY_MAX_PAYLOAD`. 159 160Other return codes from writing operation can be returned. Since the library retries on `EINTR`, 161`-EINTR` should never be returned. 162