matlab.io.datastore.DsFileReader - File-reader object for files in a datastore - MATLAB (original) (raw)
Namespace: matlab.io.datastore
File-reader object for files in a datastore
Description
The DsFileReader object enables low-level file reading access for files in your datastore.
Construction
fr = matlab.io.datastore.DsFileReader([filename](#d126e434010)) returns a DsFileReader object for read access to the file specified by filename.
fr = matlab.io.datastore.DsFileReader([filename](#d126e434010),'TextEncoding',[encoding](#d126e434051)) specifies the character encoding scheme associated with the file. Additionally, specifying encoding sets the TextEncoding property of the DsFileReader object.
Input Arguments
filename — File name
character vector | string scalar
File name, including the file extension, specified as a character vector or a string scalar. If the file is not in the current folder,filename must include a full or a relative path.
The Name property of theDsFileReader object stores the file name.
Example: 'myFile.txt'
Data Types: char | string
encoding — Character encoding scheme
'UTF-8' (default) | 'ISO-8859-1' | 'windows-1251' | 'windows-1252' | ...
Character encoding scheme associated with the file, specified as the name of a standard, character-encoding scheme listed in this table.
| 'Big5' | 'ISO-8859-1' | 'windows-847' |
|---|---|---|
| 'Big5-HKSCS' | 'ISO-8859-2' | 'windows-949' |
| 'CP949' | 'ISO-8859-3' | 'windows-1250' |
| 'EUC-KR' | 'ISO-8859-4' | 'windows-1251' |
| 'EUC-JP' | 'ISO-8859-5' | 'windows-1252' |
| 'EUC-TW' | 'ISO-8859-6' | 'windows-1253' |
| 'GB18030' | 'ISO-8859-7' | 'windows-1254' |
| 'GB2312' | 'ISO-8859-8' | 'windows-1255' |
| 'GBK' | 'ISO-8859-9' | 'windows-1256' |
| 'IBM866' | 'ISO-8859-11' | 'windows-1257' |
| 'KOI8-R' | 'ISO-8859-13' | 'windows-1258' |
| 'KOI8-U' | 'ISO-8859-15' | 'US-ASCII' |
| 'Macintosh' | 'UTF-8' | |
| 'Shift_JIS' |
The TextEncoding property of theDsFileReader object stores the value specified inencoding.
Example: 'Shift_JIS'
Data Types: char | string
Properties
Name — File name
character vector | string scalar
File name, specified as a character vector or string scalar.
Example: fr.Name returns the file name.
Data Types: char | string
Size — File size
numeric scalar
File size in bytes, returned as a numeric scalar integer.
Example: fr.Size
Data Types: double
TextEncoding — Character encoding scheme
'UTF-8' (default) | 'ISO-8859-1' | 'windows-1251' | 'windows-1252' | ...
Character encoding scheme associated with the file, specified as the name of a standard, character-encoding scheme. To set the value for theTextEncoding property, see the description of theencoding input argument.
Example: 'TextEncoding','Shift_JIS'
Position — Position pointer location
integer
Position pointer location in the file, specified as an integer. The position pointer is a zero-based integer that tracks the number of bytes from the beginning of the file.
If a file has n bytes of data, then thosen bytes are in positions 0 throughn-1.
You can set the Position property using the seek method. Calls to the read method begin reading the file from the location indicated by the Position property. When reading a file iteratively, the read method automatically updates the position pointer. Subsequent calls to the read method begin reading from the end position of the previous read operation.
Data Types: double
Methods
| hasdata | Determine if data is available to read |
|---|---|
| read | Read bytes from file |
| seek | Seek to a position in the file |
Examples
Read File Portion Specified by Starting Position and Size
Create a file-reader object for a file, seek to the desired starting position, and read a portion of the file.
Create a DsFileReader object forairlinesmall.csv.
fr = matlab.io.datastore.DsFileReader('airlinesmall.csv');
The airlinesmall.csv file has variable names at the beginning of the file. The variable names line ends at the position marked by299 bytes. To get past the variable names line, use theseek method to move the read pointer to the starting position.
seek(fr,299,'RespectTextEncoding',true);
Read the first 1000 characters.
if hasdata(fr) d = read(fr,1000,'SizeMethod','OutputSize','OutputType','char'); end
Version History
Introduced in R2017b