问题描述
最近我一直在挖掘铬代码,然后我发现了一些我无法理解的代码。文件位于 src / media / media.gyp
有人可以用简单的英文解释这一行的含义吗? 我不明白的行:
'<!@(
代码 p>
['OS!=linux',{$ b $'sources!':[
'audio / cras / audio_manager_cras.cc',
'audio / cras / audio_manager_cras.h',
'audio / cras / cras_input.cc',
'audio / cras / cras_input.h',
'audio / cras / cras_unified.cc',
'audio / cras / cras_unified.h',
],
}],
['use_pulseaudio == 1 ',{
'cflags':[
'<!@(],
'定义':[
'USE_PULSEAUDIO',
],
'条件':[
['linux_link_pulseaudio == 0',{
'定义':[
'DLOPEN_PULSEAUDIO',
],
'变量':{$ b $''generate_stubs_script':' ../tools/generate_stubs/generate_stubs.py',
'extra_header':'audio / pulse / pulse_stub_header.fragment',
'sig_files':['audio / pulse / pulse.sigs'],
参见
<!@
表示命令扩展
一个命令扩展,包含在括号内的整个字符串被传递给系统的shell。该命令的输出被分配给一个字符串值,该值随后可以在列表上下文中以与变量扩展相同的方式扩展(如果使用了@字符)。
示例:(
'!(echo filename with space.cc)',
$ b $
'libraries':[
'!@(pkg-config --libs-only-l apr-1)',
],
}
将展开至
{$ b $'sources':[
'filename with space.cc',#no @,扩展为单个字符串
],
'libraries': [#@被使用了,所以每个lib
'-lapr-1',
'-lpthread',
],
}
都有单独的列表项
I have been digging up chromium code recently, then I found piece of code that I could not understand. File is located at src/media/media.gyp
Can someone explain what this line means in plain English?
The line I don't understand :
'<!@(<(pkg-config) --cflags libpulse)',
The code :
['OS!="linux"', {
'sources!': [
'audio/cras/audio_manager_cras.cc',
'audio/cras/audio_manager_cras.h',
'audio/cras/cras_input.cc',
'audio/cras/cras_input.h',
'audio/cras/cras_unified.cc',
'audio/cras/cras_unified.h',
],
}],
['use_pulseaudio==1', {
'cflags': [
'<!@(<(pkg-config) --cflags libpulse)', # <- this line
],
'defines': [
'USE_PULSEAUDIO',
],
'conditions': [
['linux_link_pulseaudio==0', {
'defines': [
'DLOPEN_PULSEAUDIO',
],
'variables': {
'generate_stubs_script': '../tools/generate_stubs/generate_stubs.py',
'extra_header': 'audio/pulse/pulse_stub_header.fragment',
'sig_files': ['audio/pulse/pulse.sigs'],
See Command-Expansions in the gyp docs
<!@
means Command Expansions
In a command expansion, the entire string contained within the parentheses is passed to the system’s shell. The command’s output is assigned to a string value that may subsequently be expanded in list context in the same way as variable expansions if an @ character is used.
Example:
{
'sources': [
'!(echo filename with space.cc)',
],
'libraries': [
'!@(pkg-config --libs-only-l apr-1)',
],
}
will be expand to
{
'sources': [
'filename with space.cc', # no @, expands into a single string
],
'libraries': [ # @ was used, so there's a separate list item for each lib
'-lapr-1',
'-lpthread',
],
}
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