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The first command uses the AsByteStream parameter to get the stream of bytes from the file.The Raw parameter ensures that the bytes are returned as a [System.Byte]. If the Rawparameter was absent, the return value is a stream of bytes, which is interpreted byPowerShell as [System.Object].
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A warning occurs when you use the AsByteStream parameter with the Encoding parameter. TheAsByteStream parameter ignores any encoding and the output is returned as a stream of bytes.
When reading from and writing to binary files, use the AsByteStream parameter and a value of 0for the ReadCount parameter. A ReadCount value of 0 reads the entire file in a single readoperation. The default ReadCount value, 1, reads one byte in each read operation and convertseach byte into a separate object, which causes errors when you use the Set-Content cmdlet to writethe bytes to a file unless you use AsByteStream parameter.
In its first version, from 1991 to 1995, Unicode was a 16-bit encoding, but starting with Unicode 2.0 (July, 1996), the Unicode Standard has encoded characters in the range U+0000..U+10FFFF, which amounts to a 21-bit code space. Depending on the encoding form you choose (UTF-8, UTF-16, or UTF-32), each character will then be represented either as a sequence of one to four 8-bit bytes, one or two 16-bit code units, or a single 32-bit code unit.
Each UTF is reversible, thus every UTF supports lossless round tripping: mapping from any Unicode coded character sequence S to a sequence of bytes and back will produce S again. To ensure round tripping, a UTF mapping must have a mapping for all code points (except surrogate code points). This includes reserved or unassigned code points and the 66 noncharacters (including U+FFFE and U+FFFF). In addition to being lossless, UTFs are unique: any given coded character sequence will always result in the same sequence of bytes for a given UTF.
UTF-16 and UTF-32 use code units that are two and four bytes long respectively. For these UTFs, there are three sub-flavors: BE, LE and unmarked. The BE form uses big-endian byte serialization (most significant byte first), the LE form uses little-endian byte serialization (least significant byte first) and the unmarked form uses big-endian byte serialization by default, but may include a byte order mark at the beginning to indicate the actual byte serialization used. [AF]
Use UTF-8. This preserves ASCII, but not Latin-1, because the characters >127 are different from Latin-1. UTF-8 uses the bytes in the ASCII only for ASCII characters. Therefore, it works well in any environment where ASCII characters have a significance as syntax characters, e.g. file name syntaxes, markup languages, etc., but where the all other characters may use arbitrary bytes.
Use SCSU. This format compresses Unicode into 8-bit format, preserving most of ASCII, but using some of the control codes as commands for the decoder. However, while ASCII text will look like ASCII text after being encoded in SCSU, other characters may occasionally be encoded with the same byte values, making SCSU unsuitable for 8-bit channels that blindly interpret any of the bytes as ASCII characters.
Data types longer than a byte can be stored in computer memory with the most significant byte (MSB) first or last. The former is called big-endian, the latter little-endian. When data is exchanged, bytes that appear in the "correct" order on the sending system may appear to be out of order on the receiving system. In that situation, a BOM would look like 0xFFFE which is a noncharacter, allowing the receiving system to apply byte reversal before processing the data. UTF-8 is byte oriented and therefore does not have that issue. Nevertheless, an initial BOM might be useful to identify the datastream as UTF-8. [AF]
A BOM can be used as a signature no matter how the Unicode text is transformed: UTF-16, UTF-8, or UTF-32. The exact bytes comprising the BOM will be whatever the Unicode character U+FEFF is converted into by that transformation format. In that form, the BOM serves to indicate both that it is a Unicode file, and which of the formats it is in. Examples:
Number of bytes that fprintf writes, returnedas a scalar. When writing to a file, nbytes isdetermined by the character encoding. When printing data to the screen, nbytes isthe number of characters displayed on the screen.