From 754bbf7a25a8dda49b5d08ef0d0443bbf5af0e36 Mon Sep 17 00:00:00 2001 From: Craig Jennings Date: Sun, 7 Apr 2024 13:41:34 -0500 Subject: new repository --- devdocs/c/string%2Fbyte%2Fmemccpy.html | 106 +++++++++++++++++++++++++++++++++ 1 file changed, 106 insertions(+) create mode 100644 devdocs/c/string%2Fbyte%2Fmemccpy.html (limited to 'devdocs/c/string%2Fbyte%2Fmemccpy.html') diff --git a/devdocs/c/string%2Fbyte%2Fmemccpy.html b/devdocs/c/string%2Fbyte%2Fmemccpy.html new file mode 100644 index 00000000..a487a5ec --- /dev/null +++ b/devdocs/c/string%2Fbyte%2Fmemccpy.html @@ -0,0 +1,106 @@ +

memccpy

Defined in header <string.h> 
void* memccpy( void* restrict dest, const void* restrict src, int c, size_t count );
+		 (since C23)

Copies bytes from the object pointed to by src to the object pointed to by dest, stopping after any of the next two conditions are satisfied:

+

The src and dest objects are interpreted as arrays of unsigned char.

+

The behavior is undefined if any condition is met:

+

Parameters

+ + + + +
dest - pointer to the object to copy to
src - pointer to the object to copy from
c - terminating byte, converted to unsigned char at first
count - number of bytes to copy

Return value

If the byte (unsigned char)c was found, memccpy returns a pointer to the next byte in dest after (unsigned char)c. Otherwise it returns a null pointer.

+

Notes

The function is identical to the POSIX memccpy.

+

memccpy(dest, src, 0, count) behaves similar to strncpy(dest, src, count), except that the former returns a pointer to the end of the buffer written, and does not zero-pad the destination array. Thus, memccpy is useful for efficiently concatenating multiple strings.

+
char bigString[1000];
+char* end = bigString + sizeof bigString;
+ 
+char* p = memccpy(bigString, "John, ", '\0', sizeof bigString - 1);
+if (p)
+    p = memccpy(p - 1, "Paul, ", '\0', end - p);
+if (p)
+    p = memccpy(p - 1, "George, ", '\0', end - p);
+if (p)
+    p = memccpy(p - 1, "Joel ", '\0', end - p);
+if (!p)
+    end[-1] = '\0';
+ 
+puts(bigString); // John, Paul, George, Joel

Example

#include <ctype.h>
+#include <stdio.h>
+#include <string.h>
+ 
+int main(void)
+{
+    const char src[] = "Stars: Altair, Sun, Vega.";
+    const char terminal[] = {':', ' ', ',', '.', '!'};
+    char dest[sizeof src];
+    const char alt = '@';
+ 
+    for (size_t i = 0; i != sizeof terminal; ++i)
+    {
+        void* to = memccpy(dest, src, terminal[i], sizeof dest);
+ 
+        printf("Terminal '%c' (%s):\t\"", terminal[i], to ? "found" : "absent");
+ 
+        // if `terminal` character was not found - print the whole `dest`
+        to = to ? to : dest + sizeof dest;
+ 
+        for (char* from = dest; from != to; ++from)
+            putchar(isprint(*from) ? *from : alt);
+ 
+        puts("\"");
+    }
+ 
+ 
+    puts("\n" "Separate star names from distances (ly):");
+    const char *star_distance[] = {
+        "Arcturus : 37", "Vega : 25", "Capella : 43", "Rigel : 860", "Procyon : 11"
+    };
+    char names_only[64];
+    char *first = names_only;
+    char *last = names_only + sizeof names_only;
+ 
+    for (size_t t = 0; t != (sizeof star_distance) / (sizeof star_distance[0]); ++t)
+    {
+        if (first)
+            first = memccpy(first, star_distance[t], ' ', last - first);
+        else
+            break;
+    }
+ 
+    if (first)
+    {
+        *first = '\0';
+        puts(names_only);
+    }
+    else
+        puts("Buffer is too small.");
+}

Output:

+
Terminal ':' (found):   "Stars:"
+Terminal ' ' (found):   "Stars: "
+Terminal ',' (found):   "Stars: Altair,"
+Terminal '.' (found):   "Stars: Altair, Sun, Vega."
+Terminal '!' (absent):  "Stars: Altair, Sun, Vega.@"
+ 
+Separate star names from distances (ly):
+Arcturus Vega Capella Rigel Procyon

See also

+ + + + +
+
(C11)
 copies one buffer to another
(function)
+
(C95)(C11)
 copies a certain amount of wide characters between two non-overlapping arrays
(function)
+
(C11)
 moves one buffer to another
(function)
+
(C11)
 copies one string to another
(function)
+
(C11)
 concatenates two strings
(function)
+

+ © cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
+ https://en.cppreference.com/w/c/string/byte/memccpy +

+
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