From c970388b22e81a90f58fdbed195413229d89d6d7 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Fri, 20 Aug 2021 10:51:53 +0200 Subject: [PATCH] sd-id128: add compound literal love to sd_id128_to_string() + id128_to_uuid_string() --- man/rules/meson.build | 5 +- man/sd_id128_to_string.xml | 69 +++++++++++++++------------- src/libsystemd/sd-id128/id128-util.h | 2 + src/systemd/sd-id128.h | 4 +- 4 files changed, 47 insertions(+), 33 deletions(-) diff --git a/man/rules/meson.build b/man/rules/meson.build index 8c2217383a9..c6f343d8e5a 100644 --- a/man/rules/meson.build +++ b/man/rules/meson.build @@ -633,7 +633,10 @@ manpages = [ 'sd_id128_get_machine_app_specific'], ''], ['sd_id128_randomize', '3', [], ''], - ['sd_id128_to_string', '3', ['sd_id128_from_string'], ''], + ['sd_id128_to_string', + '3', + ['SD_ID128_STRING_MAX', 'SD_ID128_TO_STRING', 'sd_id128_from_string'], + ''], ['sd_is_fifo', '3', ['sd_is_mq', diff --git a/man/sd_id128_to_string.xml b/man/sd_id128_to_string.xml index 469768050bd..db64bc018d1 100644 --- a/man/sd_id128_to_string.xml +++ b/man/sd_id128_to_string.xml @@ -17,7 +17,9 @@ sd_id128_to_string + SD_ID128_TO_STRING sd_id128_from_string + SD_ID128_STRING_MAX Format or parse 128-bit IDs as strings @@ -25,9 +27,13 @@ #include <systemd/sd-id128.h> + #define SD_ID128_STRING_MAX 33U + + #define SD_ID128_TO_STRING(id) … + char *sd_id128_to_string - sd_id128_t id, char s[33] + sd_id128_t id, char s[static SD_ID128_STRING_MAX] @@ -41,47 +47,48 @@ Description - sd_id128_to_string() formats a 128-bit - ID as a character string. It expects the ID and a string array - capable of storing 33 characters. The ID will be formatted as 32 - lowercase hexadecimal digits and be terminated by a - NUL byte. + sd_id128_to_string() formats a 128-bit ID as a character string. It expects + the ID and a string array capable of storing 33 characters + (SD_ID128_STRING_MAX). The ID will be formatted as 32 lowercase hexadecimal digits + and be terminated by a NUL byte. - sd_id128_from_string() implements the reverse operation: it takes a 33 character string - with 32 hexadecimal digits (either lowercase or uppercase, terminated by NUL) and parses them - back into a 128-bit ID returned in ret. Alternatively, this call can also parse a - 37-character string with a 128-bit ID formatted as RFC UUID. If ret is passed as - NULL the function will validate the passed ID string, but not actually return it in parsed - form. + SD_ID128_TO_STRING() is a macro that wraps + sd_id128_to_string() and passes an appropriately sized buffer as second argument, + allocated as C99 compound literal. Each use will thus implicitly acquire a suitable buffer on the stack + which remains valid until the end of the current code block. This is usually the simplest way to acquire + a string representation of a 128-bit ID in a buffer that is valid in the current code block. + + sd_id128_from_string() implements the reverse operation: it takes a 33 + character string with 32 hexadecimal digits (either lowercase or uppercase, terminated by + NUL) and parses them back into a 128-bit ID returned in + ret. Alternatively, this call can also parse a 37-character string with a 128-bit + ID formatted as RFC UUID. If ret is passed as NULL the + function will validate the passed ID string, but not actually return it in parsed form. Note that when parsing 37 character UUIDs this is done strictly in Big Endian byte order, - i.e. according to RFC4122 Variant 1 - rules, even if the UUID encodes a different variant. This matches behaviour in various other Linux - userspace tools. It's probably wise to avoid UUIDs of other variant types. + i.e. according to RFC4122 Variant 1 rules, even + if the UUID encodes a different variant. This matches behaviour in various other Linux userspace + tools. It's probably wise to avoid UUIDs of other variant types. - For more information about the sd_id128_t - type see - sd-id1283. - Note that these calls operate the same way on all architectures, - i.e. the results do not depend on endianness. + For more information about the sd_id128_t type see + sd-id1283. Note that + these calls operate the same way on all architectures, i.e. the results do not depend on + endianness. - When formatting a 128-bit ID into a string, it is often - easier to use a format string for - printf3. - This is easily done using the - SD_ID128_FORMAT_STR and SD_ID128_FORMAT_VAL() macros. For - more information see + When formatting a 128-bit ID into a string, it is often easier to use a format string for + printf3. This + is easily done using the SD_ID128_FORMAT_STR and + SD_ID128_FORMAT_VAL() macros. For more information see sd-id1283. Return Value - sd_id128_to_string() always succeeds - and returns a pointer to the string array passed in. - sd_id128_from_string() returns 0 on success, in - which case ret is filled in, or a negative - errno-style error code. + sd_id128_to_string() always succeeds and returns a pointer to the string array + passed in. sd_id128_from_string() returns 0 on success, in which case + ret is filled in, or a negative errno-style error code. diff --git a/src/libsystemd/sd-id128/id128-util.h b/src/libsystemd/sd-id128/id128-util.h index 053ef0a6a83..b7327a1f070 100644 --- a/src/libsystemd/sd-id128/id128-util.h +++ b/src/libsystemd/sd-id128/id128-util.h @@ -12,6 +12,8 @@ char *id128_to_uuid_string(sd_id128_t id, char s[static ID128_UUID_STRING_MAX]); +#define ID128_TO_UUID_STRING(id) id128_to_uuid_string((id), (char[ID128_UUID_STRING_MAX]) {}) + bool id128_is_valid(const char *s) _pure_; typedef enum Id128Format { diff --git a/src/systemd/sd-id128.h b/src/systemd/sd-id128.h index f2dd7357f86..e64f3200a3b 100644 --- a/src/systemd/sd-id128.h +++ b/src/systemd/sd-id128.h @@ -34,11 +34,13 @@ union sd_id128 { uint64_t qwords[2]; }; -#define SD_ID128_STRING_MAX 33 +#define SD_ID128_STRING_MAX 33U char *sd_id128_to_string(sd_id128_t id, char s[_SD_ARRAY_STATIC SD_ID128_STRING_MAX]); int sd_id128_from_string(const char *s, sd_id128_t *ret); +#define SD_ID128_TO_STRING(id) sd_id128_to_string((id), (char[SD_ID128_STRING_MAX]) {}) + int sd_id128_randomize(sd_id128_t *ret); int sd_id128_get_machine(sd_id128_t *ret);