Nasal library/io: Difference between revisions

Jump to navigation Jump to search

Nasal library/io (view source)

Revision as of 18:46, 16 November 2016

1,979 bytes added ,  16 November 2016
Update {{func link}} form
(Update {{func link}} form)
 
(8 intermediate revisions by the same user not shown)
Line 1: Line 1:
{{WIP}}
{{Nasal Navigation|nocat=1}}
{{Nasal Navigation}}
This page contains documentation for the '''<code>io</code> namespace''' in [[Nasal]]. This namespace provides APIs for input/output (IO) operations on files. The <code>io</code> namespace is sourced from {{fgdata file|Nasal/io.nas}} and {{simgear file|simgear/nasal/iolib.c}}.
This page contains documentation for the '''<code>io</code> namespace''' in [[Nasal]]. This namespace provides APIs for input/output (IO) operations on files. The <code>io</code> namespace is sourced from {{fgdata file|Nasal/io.nas}} and {{simgear file|simgear/nasal/iolib.c}}.


Line 23: Line 22:
|text = Flushes and closes the specified file. Returns <code>'''nil'''</code>.
|text = Flushes and closes the specified file. Returns <code>'''nil'''</code>.
|param1 = file
|param1 = file
|param1text = File object as returned by {{func link|open()}}.
|param1text = File object as returned by {{func link|open()|page=this}}.
|example1 = var path = getprop("/sim/fg-root") ~ '/keyboard.xml';
|example1 = var path = getprop("/sim/fg-root") ~ '/keyboard.xml';
var file = io.open(path);
var file = io.open(path);
Line 47: Line 46:
{{Nasal doc
{{Nasal doc
|syntax = io.flush(file);
|syntax = io.flush(file);
|text = Flushes the file's buffer. This means that the contents of the buffer (a kind of temporary storage) are written to the actual file on the hard disk. Note that the buffer is also flushed when {{func link|close()}} is called.
|text = Flushes the file's buffer. This means that the contents of the buffer (a kind of temporary storage) are written to the actual file on the hard disk. Note that the buffer is also flushed when {{func link|close()|page=this}} is called.
|param1 = file
|param1 = file
|param1text = File object as returned by {{func link|open()}}.
|param1text = File object as returned by {{func link|open()|page=this}}.
|example1 = var path = getprop("/sim/fg-home") ~ '/Export/demo.txt';
|example1 = var path = getprop("/sim/fg-home") ~ '/Export/demo.txt';
var file = io.open(path, "w"); # create and open file
var file = io.open(path, "w"); # create and open file
Line 126: Line 125:
{{!-}}
{{!-}}
{{!}} <code>a+</code>
{{!}} <code>a+</code>
{{!}} Opens a file for input and output operations. Output operations will append data to the end of the file. Input operations are affected by {{func link|seek()}}, but output operations will move the position back to the end of the file. The file is created if it does not exist.
{{!}} Opens a file for input and output operations. Output operations will append data to the end of the file. Input operations are affected by {{func link|seek()|page=this}}, but output operations will move the position back to the end of the file. The file is created if it does not exist.
{{!-}}
{{!-}}
{{!}} <code>rb</code>
{{!}} <code>rb</code>
Line 144: Line 143:
{{!-}}
{{!-}}
{{!}} <code>a+b</code> ''or'' <code>ab+</code>
{{!}} <code>a+b</code> ''or'' <code>ab+</code>
{{!}} Opens a file for input and output operations, treating it as a binary file. Output operations will append data to the end of the file. Input operations are affected by {{func link|seek()}}, but output operations will move the position back to the end of the file. The file is created if it does not exist.
{{!}} Opens a file for input and output operations, treating it as a binary file. Output operations will append data to the end of the file. Input operations are affected by {{func link|seek()|page=this}}, but output operations will move the position back to the end of the file. The file is created if it does not exist.
{{!}}}
{{!}}}
|param1 = path
|param1 = path
Line 170: Line 169:
{{Nasal doc
{{Nasal doc
|syntax = io.read(file, buf, len);
|syntax = io.read(file, buf, len);
|text = Reads a given number of bytes from the given file and places those bytes into the given buffer. The bytes will be read from the position of the position indicator (this can be changed using {{func link|seek()}}). Failures are thrown as runtime errors. Returns the number of bytes successfully read.
|text = Reads a given number of bytes from the given file and places those bytes into the given buffer. The bytes will be read from the position of the position indicator (this can be changed using {{func link|seek()|page=this}}). Failures are thrown as runtime errors. Returns the number of bytes successfully read.
|param1 = file
|param1 = file
|param1text = File object as returned by {{func link|open()}}.
|param1text = File object as returned by {{func link|open()|page=this}}.
|param2 = buf
|param2 = buf
|param2text = Buffer to read bytes into. A new buffer can be created using <code>bits.buf(size)</code>. Must not be smaller than '''len'''.  
|param2text = Buffer to read bytes into. A new buffer can be created using <code>bits.buf(size)</code>. Must not be smaller than '''len'''.  
Line 191: Line 190:
{{Nasal doc
{{Nasal doc
|syntax = io.read_airport_properties(icao, fname[, target]);
|syntax = io.read_airport_properties(icao, fname[, target]);
|version = 2.4
|commit = {{fgdata commit|d4fb11|t=commit}}
|text = Loads an airport-related XML file. Paths will be concatenated in the following form: <tt>''[[$FG_SCENERY]]/Airports/'''''i'''''/'''''c'''''/'''''a'''''/'''''icao'''''.'''''fname'''''.xml''</tt>. Returns the data as a <code>props.Node</code> object or <code>'''nil'''</code> on error. Note that the file ''must'' be in the [[PropertyList XML files|PropertyList]] format, or else the function will fail.
|text = Loads an airport-related XML file. Paths will be concatenated in the following form: <tt>''[[$FG_SCENERY]]/Airports/'''''i'''''/'''''c'''''/'''''a'''''/'''''icao'''''.'''''fname'''''.xml''</tt>. Returns the data as a <code>props.Node</code> object or <code>'''nil'''</code> on error. Note that the file ''must'' be in the [[PropertyList XML files|PropertyList]] format, or else the function will fail.
|param1 = icao
|param1 = icao
Line 245: Line 246:
|text = Reads and returns a single line from the file, advancing the position indicator. Accepts different {{wikipedia|newline}} types, including {{abbr|LF|line feed}}, {{abbr|CR|carriage return}}, and CR+LF. Does not include the EOL character(s) in the returned string. End of file or an error is signaled by returning <code>'''nil'''</code>.
|text = Reads and returns a single line from the file, advancing the position indicator. Accepts different {{wikipedia|newline}} types, including {{abbr|LF|line feed}}, {{abbr|CR|carriage return}}, and CR+LF. Does not include the EOL character(s) in the returned string. End of file or an error is signaled by returning <code>'''nil'''</code>.
|param1 = file
|param1 = file
|param1text = File object as returned by {{func link|open}}.
|param1text = File object as returned by {{func link|open()|page=this}}.
|example1 = var path = getprop("/sim/fg-root") ~ '/Nasal/bits.nas';
|example1 = var path = getprop("/sim/fg-root") ~ '/Nasal/bits.nas';
var file = io.open(path);
var file = io.open(path);
Line 281: Line 282:
|text = Moves the pointer position to a specified place.
|text = Moves the pointer position to a specified place.
|param1 = file
|param1 = file
|param1text = File object as returned by {{func link|open()}}.
|param1text = File object as returned by {{func link|open()|page=this}}.
|param2 = position
|param2 = position
|param2text = Number of bytes offset from '''whence''' as an integer. If '''whence''' is {{func link|SEEK_SET}}, this cannot be negative.
|param2text = Number of bytes offset from '''whence''' as an integer. If '''whence''' is {{func link|SEEK_SET|page=this}}, this cannot be negative.
|param3 = whence
|param3 = whence
|param3text = Specifies position to set the offset from. Must be one of {{func link|SEEK_SET}} (beginning of file), {{func link|SEEK_END}} (end of file), or {{func link|SEEK_CUR}} (current pointer position).
|param3text = Specifies position to set the offset from. Must be one of {{func link|SEEK_SET|page=this}} (beginning of file), {{func link|SEEK_END|page=this}} (end of file), or {{func link|SEEK_CUR|page=this}} (current pointer position).
|example1 = var path = getprop("/sim/fg-root") ~ '/Nasal/geo.nas';
|example1 = var path = getprop("/sim/fg-root") ~ '/Nasal/geo.nas';
var file = io.open(path, "r"); # open file
var file = io.open(path, "r"); # open file
Line 339: Line 340:
|text = Returns the current pointer position of the file.
|text = Returns the current pointer position of the file.
|param1 = file
|param1 = file
|param1text = File object as returned by {{func link|open()}}.
|param1text = File object as returned by {{func link|open()|page=this}}.
|example1 = var path = getprop("/sim/fg-root") ~ '/Nasal/geo.nas';
|example1 = var path = getprop("/sim/fg-root") ~ '/Nasal/geo.nas';
var file = io.open(path);
var file = io.open(path);
Line 352: Line 353:
|text = Writes a string to a given file and returns the number of bytes successfully written.
|text = Writes a string to a given file and returns the number of bytes successfully written.
|param1 = file
|param1 = file
|param1text = File object as returned by {{func link|open()}}.
|param1text = File object as returned by {{func link|open()|page=this}}.
|param2 = string
|param2 = string
|param2text = String to write to the file.
|param2text = String to write to the file.
{{tip|It is good practice to make sure that all lines, including the last one, end in a newline (<code>\n</code>). This will especially help if you will be calling {{func link|readln()}} on the file later.}}
{{tip|It is good practice to make sure that all lines, including the last one, end in a newline (<code>\n</code>). This will especially help if you will be calling {{func link|readln()|page=this}} on the file later.}}
|example1 = var path = getprop("/sim/fg-home") ~ '/Export/demo.txt';
|example1 = var path = getprop("/sim/fg-home") ~ '/Export/demo.txt';
var file = io.open(path, "wb"); # open in write mode
var file = io.open(path, "wb"); # open in write mode
Line 364: Line 365:


=== write_properties() ===
=== write_properties() ===
Write XML file in FlightGear's native <PropertyList> format.  
{{Nasal doc
Returns the filename on success or nil on error. If the source is a props.Node that refers to a node in the main tree,  
|syntax = io.write_properties(path, prop);
then the data are directly written from the tree, yielding a more accurate result.
|text = Writes nodes from the [[Property Tree]] to an XML file in FlightGear's [[PropertyList XML files|PropertyList]] format. If the file does not exist, it will be created. If it does, all contents will be overwritten. Returns the filename on success or <code>'''nil'''</code> on error.
Otherwise the data need to be copied first, which may slightly change node types (FLOAT becomes DOUBLE etc.)
|param1 = path
<syntaxhighlight lang="nasal">
|param1text = Path of the file to write to as a string. If it does not have a <tt>.xml</tt> extension, <tt>.xml</tt> will be added to it.
Usage:  io.write_properties(<filename>, <props.Node or property-path>);
|param2 = prop
</syntaxhighlight>
|param2text = Either a property path or a <code>props.Node</code> object. Note that, when the latter is used, results will be more accurate if it refers to a node in the Property Tree, otherwise the node will have to be copied, which may change the node type.
Examples:
|example1 = var path = getprop("/sim/fg-home") ~ '/Export/demo.xml';
<syntaxhighlight lang="nasal">
var prop = "/position";
var data = props.Node.new({ a:1, b:2, c:{ d:3, e:4 } });  
print(io.write_properties(path, prop));
io.write_properties("/tmp/foo.xml", data);              
|example2 = var path = getprop("/sim/fg-home") ~ '/Export/demo.xml';
io.write_properties("/tmp/foo.xml", "/sim/model");      
var prop = props.globals.getNode("position");
</syntaxhighlight>
print(io.write_properties(path, prop));
|example3 = var path = getprop("/sim/fg-home") ~ '/Export/demo.xml';
var tree = {
    "a": 12.34,
    "b": "Hello, World!",
    "c": {
        "d": [1, 2, 3]
    }
};
var prop = props.Node.new(tree);
print(io.write_properties(path, prop));
}}


=== writexml() ===
=== writexml() ===
Writes a property tree as returned by readxml() to a file. Children 
{{Nasal doc
with name starting with <prefix> are again turned into attributes of 
|syntax = io.basename(path, node[, indent[, prefix]]);
their parent. <node> must contain exactly one child, which will      
|text = Writes a node structure to an XML file.
become the XML file's outermost element.                            
|param1 = path
<syntaxhighlight lang="nasal">
|param1text = Path of the file to write to as a string. If it does not have a <tt>.xml</tt> extension, <tt>.xml</tt> will be added to it.
Usage: io.writexml(path, node[,indent = "\t"][, prefix = "___"]);
|param2 = node
</syntaxhighlight>
|param2text = <code>props.Node</code> object containing the data to write to the file. Attributes should be included as child nodes with a certain '''prefix'''. See also {{func link|readxml()|page=this}}. It must also have just one root node.
<syntaxhighlight lang="nasal">
|param3 = indent
io.writexml(path, node, indent,prefix);
|param3text = Optional string specifying what characters should be used to indent lines. Defaults to one horizontal tab character (<tt>\t</tt>).
</syntaxhighlight>
|param4 = prefix
|param4text = Optional string specifying what prefixes attributes will have.
|example1 = var path = getprop("/sim/fg-home") ~ '/Export/demo.xml';
var tree = {
    "source": {
        ___type: "book", # will become an attribute
        "title": "The Grand Book of Code",
        "author-last": "Echter",
        "author-first": "William C.",
        "year": "2011",
        "publisher": "Pen Publishers",
        "city": "Manchester"
    }
};
var node = props.Node.new(tree);
io.writexml(path, node);
|example2 = var path = getprop("/sim/fg-home") ~ '/Export/demo.xml';
var tree = {
    "source": {
        _attr_type: "book",
        "title": "The Grand Book of Code",
        "author-last": "Echter",
        "author-first": "William C.",
        "year": "2011",
        "publisher": "Pen Publishers",
        "city": "Manchester"
    }
};
var node = props.Node.new(tree);
io.writexml(path, node, "  ", "_attr_"); # indent using two spaces
}}


== Variables ==
== Variables ==
Line 394: Line 436:
{{Nasal doc
{{Nasal doc
|syntax = io.SEEK_CUR;
|syntax = io.SEEK_CUR;
|text = Used with {{func link|seek()}}. Means the offset will be counted from the current pointer postion.
|text = Used with {{func link|seek()|page=this}}. Means the offset will be counted from the current pointer postion.
}}
}}
=== SEEK_END ===
=== SEEK_END ===
{{Nasal doc
{{Nasal doc
|syntax = io.SEEK_END;
|syntax = io.SEEK_END;
|text = Used with {{func link|seek()}}. Means the offset will be counted from the end of the file.
|text = Used with {{func link|seek()|page=this}}. Means the offset will be counted from the end of the file.
}}
}}
=== SEEK_SET ===
=== SEEK_SET ===
{{Nasal doc
{{Nasal doc
|syntax = io.SEEK_SET;
|syntax = io.SEEK_SET;
|text = Used with {{func link|seek()}}. Means the offset will be counted from the beginning of the file.
|text = Used with {{func link|seek()|page=this}}. Means the offset will be counted from the beginning of the file.
}}
}}


[[Category:Nasal]]
{{Nasal namespaces}}
Retrieved from "https://wiki.flightgear.org/Special:MobileDiff/105629...105940"

Navigation menu