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add support for environment variable LZ4_CLEVEL

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This commit is contained in:
Yann Collet
2024-07-08 01:53:16 +02:00
parent 3b2452e5b7
commit c78899a3a2
4 changed files with 37 additions and 8 deletions
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9
programs/README.md
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@@ -27,6 +27,7 @@ The makefile offer several targets for various use cases:
These variables are read by the preprocessor at compilation time. They influence executable behavior, such as default starting values, and are exposed from `programs/lz4conf.h`. These variables can manipulated by any build system.
Assignment methods vary depending on environments.
On a typical `posix` + `gcc` + `make` setup, they can be defined with `CPPFLAGS=-DVARIABLE=value` assignment.
- `LZ4_CLEVEL_DEFAULT`: default compression level when none provided. Default is `1`.
- `LZ4IO_MULTITHREAD`: enable multithreading support. Default is disabled.
- `LZ4_NBWORKERS_DEFAULT`: default nb of worker threads used in multithreading mode (can be overridden with command `-T#`).
Default is `0`, which means "auto-determine" based on local cpu.
@@ -37,11 +38,13 @@ On a typical `posix` + `gcc` + `make` setup, they can be defined with `CPPFLAGS=
#### Environment Variables
It's possible to pass some parameters to `lz4` via environment variables.
This can be useful in situations where `lz4` is known to be invoked (from a script for example) but there is no way to pass `lz4` parameters to influence the compression session.
This can be useful in situations where `lz4` is known to be invoked (from within a script for example) but there is no way to pass `lz4` parameters to influence the compression session.
The environment variable has higher priority than binary default, but lower priority than corresponding runtime command.
When set as global environment variables, it can be a way to enforce personalized defaults different from the binary set ones.
When set as global environment variables, it can enforce personalized defaults different from the binary set ones.
`LZ4_NBWORKERS` can be used to specify a default number of threads that `lz4` will use for compression (binary default is generally `0`, which means auto-determined based on local cpu). This functionality is only relevant when `lz4` is compiled with multithreading support. The maximum number of workers is capped at `LZ4_NBWORKERS_MAX` (`200` by default).
`LZ4_CLEVEL` can be used to specify a default compression level that `lz4` employs for compression when no other compression level is specified on command line. Executable default is generally `1`.
`LZ4_NBWORKERS` can be used to specify a default number of threads that `lz4` will employ for compression. Executable default is generally `0`, which means auto-determined based on local cpu. This functionality is only relevant when `lz4` is compiled with multithreading support. The maximum number of workers is capped at `LZ4_NBWORKERS_MAX` (`200` by default).
### Aggregation of parameters
The `lz4` CLI supports aggregation for short commands. For example, `-d`, `-q`, and `-f` can be joined into `-dqf`.

9
programs/lz4.1.md
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@@ -250,11 +250,14 @@ only the latest one will be applied.
It's possible to pass some parameters to `lz4` via environment variables.
This can be useful in situations where `lz4` is known to be invoked (from a script for example) but there is no way to pass `lz4` parameters to influence the compression session.
The environment variable has higher priority than binary default, but lower priority than corresponding runtime command.
When set as global environment variables, it can be a way to enforce personalized defaults different from the binary set ones.
The environment variable has higher priority than executable default, but lower priority than corresponding runtime command.
When set as global environment variables, it can be a way to enforce personalized defaults different from the executable set ones.
* `LZ4_CLEVEL`:
specify a default compression level that `lz4` employs for compression when no other compression level is specified on command line. Executable default is generally `1`.
* `LZ4_NBWORKERS`:
specify a default number of threads that `lz4` will employ for compression (binary default is generally `0`, which means auto-determined based on local cpu). This functionality is only relevant when `lz4` is compiled with multithreading support. The maximum number of workers is capped at `LZ4_NBWORKERS_MAX` (`200` by default).
specify a default number of threads that `lz4` will employ for compression. Executable default is generally `0`, which means auto-determined based on local cpu. This functionality is only relevant when `lz4` is compiled with multithreading support. The maximum number of workers is capped at `LZ4_NBWORKERS_MAX` (`200` by default).
BUGS

17
programs/lz4cli.c
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@@ -370,10 +370,25 @@ static unsigned init_nbWorkers(void)
return LZ4_NBWORKERS_DEFAULT;
}
#define ENV_CLEVEL "LZ4_CLEVEL"
static int init_cLevel(void)
{
const char* const env = getenv(ENV_CLEVEL);
if (env != NULL) {
const char* ptr = env;
if ((*ptr>='0') && (*ptr<='9')) {
return (int)readU32FromChar(&ptr);
}
DISPLAYLEVEL(2, "Ignore environment variable setting %s=%s: not a valid unsigned value \n", ENV_CLEVEL, env);
}
return LZ4_CLEVEL_DEFAULT;
}
int main(int argCount, const char** argv)
{
int argNb,
cLevel=1,
cLevel=init_cLevel(),
cLevelLast=-10000,
legacy_format=0,
forceStdout=0,

10
programs/lz4conf.h
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@@ -26,7 +26,15 @@
#define LZ4CONF_H_32432
/* Determines if multithreading is enabled or not */
/* Default compression level.
* Can be overridden by environment variable LZ4_CLEVEL.
* Can be overridden at runtime using -# command */
#ifndef LZ4_CLEVEL_DEFAULT
# define LZ4_CLEVEL_DEFAULT 1
#endif
/* Determines if multithreading is enabled or not
* Default: disabled */
#ifndef LZ4IO_MULTITHREAD
# ifdef _WIN32
/* Windows support Completion Ports */