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@Yoric

Yoric/gist:1481186

Created Dec 15, 2011
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Working out the kinks of OS.File
//1. Reading a string from an unopened file
/**
* @param {string|OS.Path} aSource The file to read
*
* @return {Promise} The promise of a string. In case of error, the promise is
* rejected and holds the exception.
*/
function readAll(aSource) {
return OS.File.read(aSource).just(function() {
return this.readString();
});
}
//2. Writing a string to a new file.
/**
* @param {string|OS.Path} aDest The file to write
*
* @return {Promise} The promise of the number of bytes written. In case of
* error, the promise is rejected and holds the exception.
*/
function dumpTo(aContent, aDest) {
return OS.File.truncateC(aDest).just(function() {
this.writeString(aContent);
});
}
// or, alternatively, without |just|,
function dumpTo(aContent, aDest) {
let file;
return OS.File.truncateC(aDest).soon(function(aFile) {
file = aFile;
return file.writeString(aContent);
}).always(function(aStatus) {
file.close();
});
}
//3. Copying an unopened file to another by reading all and writing all
function copy(aSource, aDest) {
return OS.File.read(aSource).
just(OS.File.prototype.readString).
soon(function(aContents) {
OS.File.truncateC(aDest).
return just(OS.File.prototype.writeString, aContents);
});
}
//4. In the future, possibly, a more reasonable copy operation, by chunks
function copy(aSource, aDest, aChunkSize) {
//Open both files asynchronously
return Promise.group([ OS.File.read(aSourceName),
OS.File.truncateC(aDestName) ]).
soon(function(files) {
let [source, dest] = files;
//Connect streams
let reader = source.readStringStream(aChunkSize);
let writer = dest.writeStringStream();
return OS.File.pump(reader, writer).
//Don't forget closing
always(source.close).
always(dest.close);
});
}
//Note: |readStringStream|, |writeStringStream| and |OS.File.pump|
//do not exist yet
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