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Diffstat (limited to 'src/couchdb/couch_config_writer.erl')
| -rw-r--r-- | src/couchdb/couch_config_writer.erl | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/src/couchdb/couch_config_writer.erl b/src/couchdb/couch_config_writer.erl new file mode 100644 index 00000000..6e93c131 --- /dev/null +++ b/src/couchdb/couch_config_writer.erl @@ -0,0 +1,147 @@ +% Licensed under the Apache License, Version 2.0 (the "License"); you may not +% use this file except in compliance with the License. You may obtain a copy of +% the License at +% +% http://www.apache.org/licenses/LICENSE-2.0 +% +% Unless required by applicable law or agreed to in writing, software +% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +% License for the specific language governing permissions and limitations under +% the License. + +%% @doc Saves a Key/Value pair to a ini file. The Key consists of a Module +%% and Variable combination. If that combination is found in the ini file +%% the new value replaces the old value. If only the Module is found the +%% Variable and value combination is appended to the Module. If the Module +%% does not yet exist in the ini file, it is added and the Variable/Value +%% pair is appended. +%% @see couch_config + +-module(couch_config_writer). +-include("couch_db.hrl"). + +-export([save_to_file/2]). + +%% @spec save_to_file( +%% Config::{{Module::string(), Variable::string()}, Value::string()}, +%% File::filename()) -> ok +%% @doc Saves a Module/Key/Value triple to the ini file File::filename() +save_to_file({{Module, Variable}, Value}, File) -> + + ?LOG_DEBUG("saving to file '~s', Congif: '~p'", [File, {{Module, Variable}, Value}]), + + % open file and create a list of lines + {ok, Stream} = file:read_file(File), + OldFileContents = binary_to_list(Stream), + {ok, Lines} = regexp:split(OldFileContents, "\r\n|\n|\r|\032"), + + % prepare input variables + ModuleName = "[" ++ Module ++ "]", + VariableList = Variable, + + % produce the contents for the config file + NewFileContents = + case NewFileContents2 = save_loop({{ModuleName, VariableList}, Value}, Lines, "", "", []) of + % we didn't change anything, that means we couldn't find a matching + % [ini section] in which case we just append a new one. + OldFileContents -> + append_new_ini_section({{ModuleName, VariableList}, Value}, OldFileContents); + _ -> + NewFileContents2 + end, + + % do the save, close the config file and get out + save_file(File, NewFileContents), + file:close(Stream), + ok. + +%% @doc Iterates over the lines of an ini file and replaces or adds a new +%% configuration directive. +save_loop({{Module, Variable}, Value}, [Line|Rest], OldCurrentModule, Contents, DoneVariables) -> + + % if we find a new [ini section] (Module), save that for reference + NewCurrentModule = parse_module(Line, OldCurrentModule), + + % if the current Module is the one we want to change, try to match + % each line with the Variable + NewContents = case Module of + NewCurrentModule -> + % see if the current line matches the variable we want to substitute + case parse_variable(Line, Variable, Value) of + % nope, return original line + nomatch -> + DoneVariables2 = DoneVariables, + Line; + % got em! return new line + NewLine -> + DoneVariables2 = [Variable|DoneVariables], + NewLine + end; + % if the variable we want to change couldn't be replaced, we append it + % in the proper module section + OldCurrentModule -> + case lists:member(Variable, DoneVariables) of + false -> + DoneVariables2 = [Variable|DoneVariables], + Variable ++ "=" ++ Value ++ "\n" ++ Line; + true -> + DoneVariables2 = DoneVariables, + Line + end; + % otherwise we just print out the original line + _ -> + DoneVariables2 = DoneVariables, + Line + end, + % clumsy way to only append a newline character + % if the line is not empty. We need this to not + % avoid haveing a newline inserted at the top + % of the target file each time we save it. + Contents2 = case Contents of "" -> ""; _ -> Contents ++ "\n" end, + + % go to next line + save_loop({{Module, Variable}, Value}, Rest, NewCurrentModule, Contents2 ++ NewContents, DoneVariables2); + +save_loop(_Config, [], _OldModule, NewFileContents, _DoneVariable) -> + % we're out of new lines, just return the new file's contents + NewFileContents. + +append_new_ini_section({{ModuleName, Variable}, Value}, OldFileContents) -> + OldFileContents ++ "\n\n" ++ ModuleName ++ "\n" ++ Variable ++ "=" ++ Value ++ "\n". + +%% @spec parse_module(Lins::string(), OldModule::string()) -> string() +%% @doc Tries to match a line against a pattern specifying a ini module or +%% section ("[Module]"). Returns OldModule if no match is found. +parse_module(Line, OldModule) -> + case regexp:match(Line, "^\\[([a-zA-Z0-9_-]*)\\]$") of + nomatch -> + OldModule; + {error, Error} -> + io:format("ini file regex error module: '~s'~n", [Error]), + OldModule; + {match, Start, Length} -> + string:substr(Line, Start, Length) + end. + +%% @spec parse_variable(Line::string(), Variable::string(), Value::string()) -> +%% string() | nomatch +%% @doc Tries to match a variable assignment in Line. Returns nomatch if the +%% Variable is not found. Returns a new line composed of the Variable and +%% Value otherwise. +parse_variable(Line, Variable, Value) -> + case regexp:match(Line, "^" ++ Variable ++ "=") of + nomatch -> + nomatch; + {error, Error}-> + io:format("ini file regex error variable: '~s'~n", [Error]), + nomatch; + {match, _Start, _Length} -> + Variable ++ "=" ++ Value + end. + +%% @spec save_file(File::filename(), Contents::string()) -> +%% ok | {error, Reason::string()} +%% @doc Writes Contents to File +save_file(File, Contents) -> + file:write_file(File, list_to_binary(Contents)).
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