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--- uphp:functions:fwrite [2017/05/08 14:26]
jeff
+++ uphp:functions:fwrite [2021/09/13 05:57] (current)
@@ Line 7: / Line 7: @@
 ====Description====
-<well size="sm">
+<well size="sm"><html>
-<html>
 <span style="font-size:125%;color:green">int
 <span style="color:black">fwrite (
@@ Line 15: / Line 14: @@
 <span style="color:green">mixed
 <span style="color:blue">$data
-<span style="color:black">)
+<span style="color:black">[,
-</html>
+<span style="color:green">int
-</well>
+<span style="color:blue">$length<span style="color:black">]
+)
+</html></well>
-This function performs a binary-safe write of strings or bytes specified by integers to a previously opened resource((<html>This function is similar to the mainline PHP function, but with the addition of the ability to write bytes specified as an <b><span style="color:green">integer<span style="color:black"></b>, and the ability to write <b><span style="color:green">string<span style="color:black"></b> or <b><span style="color:green">integer<span style="color:black"></b> data from an <b><span style="color:green">array<span style="color:black"></b>. Both of these capabilities simplify programming in uPHP for the Wattmon: data to be written can be specified as an <b><span style="color:green">int<span style="color:black"></b> byte value instead of a string, or a series of writes of either type can be combined into one statement by the use of an <b><span style="color:green">array<span style="color:black"></b>.</html>))
+This function performs a binary-safe write of strings or bytes specified by integers to a previously opened resource((<html>This function is similar to the mainline PHP function, but with the addition of the ability to write bytes specified as an <b><span style="color:green">integer<span style="color:black"></b>, and the ability to write <b><span style="color:green">string<span style="color:black"></b> or <b><span style="color:green">integer<span style="color:black"></b> data from an <b><span style="color:green">array<span style="color:black"></b></html>. Both of these capabilities simplify programming in uPHP for the [[hardware:wattmons|Wattmon]]: data to be written can be specified as an <html><b><span style="color:green">int<span style="color:black"></b> byte value instead of a string, or a series of writes of either type can be combined into one statement by the use of an <b><span style="color:green">array<span style="color:black"></b>.</html>))
 ====Parameters====
@@ Line 31: / Line 32: @@
   * <html><b><span style="color:green">array<span style="color:black"></b> - A series of <b><span style="color:green">string<span style="color:black"></b> and/or <b><span style="color:green">int<span style="color:black"></b> byte data to write - useful for writing several strings and/or binary data to a resource</html>((<html>If the <b><span style="color:blue">data<span style="color:black"></b> is type <b><span style="color:green">array<span style="color:black"></b> and the array contains integers that are not in the range from 0 to 255 (8 bits) then multiple bytes will be written (up to 4 bytes or 32 bits, which may be unexpected). Array elements that are type <b><span style="color:green">float<span style="color:black"></b> or <b><span style="color:green">array<span style="color:black"></b> will always write 0 bytes.</html>))
-====Return Value====
+<html><b><span style="color:blue">$length<span style="color:black"></b></html>:  Optional length of buffer - automatically calculated for strings if not specified
+====Return Values====
 <html><b><span style="color:green">Integer<span style="color:black"></b></html> **number of bytes successfully written**
@@ Line 68: / Line 72: @@
 ABCDEF
 Line 3
+</code>
+====Note====
+When working with binary data such as data read from a file using fread(), make sure to pass the variable as a pointer using the & symbol.  Otherwise a copy of the string will be made but will only be copied until the first NULL character is found.
+For example, this script will make an exact copy of the contents of file original.bin into copy.bin:
+<code php>
+<?
+  $fo = fopen("/original.bin","r");
+  $fh = fopen("/copy.bin","w");
+  $len = filesize($fo);
+  while ($len) {
+     if ($len>512) {
+       $buflen=512;
+     } else $buflen=$len;
+     $data = fread($fo,512);
+     // make sure you also specify the optional file size
+     // or else it will use the length of the string (till the first null).
+     // also, pass the variable by reference
+     fwrite($fh,&$data,512);
+     $len = $len - $buflen;
+  }
+  fclose($fh);
+  fclose($fo);
+?>
 </code>

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