mirror of https://github.com/odrling/Aegisub
215 lines
4.9 KiB
Plaintext
215 lines
4.9 KiB
Plaintext
Automation 4 File Stream interface
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This file describes the interface used for reading and writing files in
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Automation 4. This includes text encoding conversion routines.
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---
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About encodings
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All file streams always have a text encoding. The default encoding is
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determined by the user, before the import/export operation is started.
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All string operations on a stream follow the current encoding. You can
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change the encoding during reading/writing, and the change will only take
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effect from that point on.
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You can perform binary IO by setting the encoding to 'binary' and using
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strings consisting only of codepoints 0 to 255.
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---
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Output File Stream user data object
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This object is passed to functions operating on an Output File Stream.
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---
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Input File Stream user data object
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This object is passed to functions operating on an Input File Stream.
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---
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Getting text encoding
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This function returns a string describing the current text encoding used for
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a file stream.
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function aegisub.fstream.get_encoding(stream)
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@stream (user data)
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The Input File Stream or Output File Stream to get the encoding for.
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Returns: String describing the encoding. This string can be used for setting
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the encoding later.
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---
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Setting text encoding
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This function changes the current text encoding used for a file stream.
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function aegisub.fstream.set_encoding(stream, encoding)
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@stream (user data)
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The Input File Stream or Output File Stream to change the encoding for.
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@encoding (string)
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The new encoding to use.
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Returns: String describing the old encoding.
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---
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File Pointer operations
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function aegisub.fstream.tell(stream)
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@stream (user data)
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The Input File Stream or Output File Stream get position of.
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Returns: Number, the number of bytes since the beginning of the file.
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function aegisub.fstream.seek(stream, length)
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@stream (user data)
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The Input File Stream or Output File Stream to seek in.
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@length (number)
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Number of bytes to skip. This can be negative.
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You can only seek backwards in an Output File Stream, and doing so truncates
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the file.
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Returns: nothing.
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function aegisub.fstream.reset(stream)
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Resets the file pointer to the start of the file. Truncates an Output File
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Stream to zero bytes.
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@stream (user data)
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The Input File Stream or Output File Stream to seek in.
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Returns: nothing.
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---
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Reading text
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All these functions assume the file is in the current encoding specified.
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function aegisub.fstream.skip_utf_bom(stream, change_encoding)
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This function has undefined behaviour unless called as the first
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read-operation on the stream.
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It detects whether the file stream starts with an UTF Byte Order Mark, skips
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the number of bytes used by that BOM, and optionally changes the current file
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encoding to match the detected BOM.
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@stream (user data)
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The Input File Stream to read from.
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@change_encoding (boolean)
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If true, change encoding to match the detected BOM.
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Returns: Boolean, whether a BOM was detected or not.
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function aegisub.fstream.read(stream, length)
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Read a number of characters from a file.
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@stream (user data)
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The Input File Stream to read from.
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@length (number)
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Number of characters to read. If this is zero, no data are read. If this
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is larger than the number of characters available, data are read until the
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end of file.
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Returns: String, the string read from the file.
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function aegisub.fstream.read_bytes(stream, length)
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Read a number of bytes from a file and convert to a string.
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@stream (user data)
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The Input File Stream to read from.
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@length (number)
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The number of bytes to read.
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Returns: String, best-effort converted from the bytes read.
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function aegisub.fstream.read_line(stream, include_newline)
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Read until next newline in the file. A newline is defined asone of these
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sequences of Unicode codepoints in the decoded text:
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0x0A ("\n")
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0x0D ("\r")
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0x0D 0x0A ("\r\n")
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The sequence "\n\r" is interpreted as two newlines, ie. a newline, a blank
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line and yet another newline.
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@stream (user data)
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The Input File Stream to read from.
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@include_newline (boolean)
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If true, include the newline character(s) in the returned string.
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Returns: String.
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---
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Writing text
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All these functions assume the file is in the current encoding specified.
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function aegisub.fstream.write_utf_bom(stream)
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This function will corrupt your file if used anywhere else than on position 0.
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Write the correct UTF BOM character to the file, or nothing if not currently
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in an UTF encoding.
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@stream (user data)
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The Output File Stream to write the BOM to.
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Returns: nothing.
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function aegisub.fstream.write(stream, text)
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Write a string to a file.
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@stream (user data)
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The Output File Stream to write to.
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@text (string)
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The text to write.
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Returns: nothing.
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function aegisub.fstream.write_line(stream, text)
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Write a string to a file, followed by an "\r\n" newline.
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@stream (user data)
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The Output File Stream to write to.
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@text (string)
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The text to write.
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Returns: nothing.
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---
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