fs: add hash compute method

docs/markdown/Fs-module.md

@@ -32,6 +32,14 @@ name exists on the file system. This method follows symbolic links.
 Takes a single string argument and returns true if the path pointed to
 by the string is a symbolic link.
 
+## File Parameters
+
+### hash
+
+The `hash` method computes the requested hash sum of a file.
+The available hash methods include: md5, sha1, sha224, sha256, sha384, sha512.
+
+
 ## Filename modification
 
 ### with_suffix

mesonbuild/modules/fs.py

@@ -13,8 +13,10 @@
 # limitations under the License.
 
 import typing
+import hashlib
 from pathlib import Path, PurePath
 
+from .. import mlog
 from . import ExtensionModule
 from . import ModuleReturnValue
 from ..mesonlib import MesonException
@@ -55,6 +57,22 @@ class FSModule(ExtensionModule):
     def is_dir(self, state: 'ModuleState', args: typing.Sequence[str], kwargs: dict) -> ModuleReturnValue:
         return self._check('is_dir', state, args)
 
+    @stringArgs
+    @noKwargs
+    def hash(self, state: 'ModuleState', args: typing.Sequence[str], kwargs: dict) -> ModuleReturnValue:
+        if len(args) != 2:
+            MesonException('method takes exactly two arguments.')
+        file = Path(state.source_root) / state.subdir / Path(args[0]).expanduser()
+        if not file.is_file():
+            raise MesonException('{} is not a file and therefore cannot be hashed'.format(file))
+        try:
+            h = hashlib.new(args[1])
+        except ValueError:
+            raise MesonException('hash algorithm {} is not available'.format(args[1]))
+        mlog.debug('computing {} sum of {} size {} bytes'.format(args[1], file, file.stat().st_size))
+        h.update(file.read_bytes())
+        return ModuleReturnValue(h.hexdigest(), [])
+
     @stringArgs
     @noKwargs
     def with_suffix(self, state: 'ModuleState', args: typing.Sequence[str], kwargs: dict) -> ModuleReturnValue:

test cases/common/227 fs module/meson.build

@@ -47,4 +47,12 @@ new_check = is_windows ? 'j:\\foo\\bar.ini' : '/foo/bar.ini'
 new = fs.with_suffix(original, '.ini')
 assert(new == new_check, 'absolute path with_suffix failed')
 
+# -- hash
+
+md5 = fs.hash('subdir/subdirfile.txt', 'md5')
+sha256 = fs.hash('subdir/subdirfile.txt', 'sha256')
+assert(md5 == 'd0795db41614d25affdd548314b30b3b', 'md5sum did not match')
+assert(sha256 == 'be2170b0dae535b73f6775694fffa3fd726a43b5fabea11b7342f0605917a42a', 'sha256sum did not match')
+
+
 subdir('subdir')