add man pages for fmt_copybytes and fmt_copybytes_sizeof_minus1

fmt.h

@@ -129,10 +129,7 @@ static inline size_t fmt_copybytes(char* dest,const char* src,size_t n) {
  *   fmt_copybytes_sizeof_minus1(dest, "\x01\x02\x03\x04");
  * since we are technically passing a string, sizeof will include the
  * finishing 0 byte which we neither need nor want */
-static inline size_t fmt_copybytes_sizeof_minus1(char* dest,const char* src) {
-  if (dest) byte_copy(dest,sizeof(src)-1,src);
-  return sizeof(src)-1;
-}
+#define fmt_copybytes_sizeof_minus1(dest,src) fmt_copybytes(dest,src,sizeof(src)-1)
 
 /* "foo" -> "  foo"
  * write padlen-srclen spaces, if that is >= 0.  Then copy srclen

fmt/fmt_copybytes.3

@@ -0,0 +1,15 @@
+.TH fmt_copybytes 3
+.SH NAME
+fmt_copybytes \- write binary data
+.SH SYNTAX
+.B #include <libowfat/fmt.h>
+
+size_t \fBfmt_copybytes\fP(char *\fIdest\fR,const char *\fIsource\fR, size_t limit);
+.SH DESCRIPTION
+fmt_copybytes copies \fIlimit\fP bytes from \fIsource\fP to \fIdest\fP and returns \fIlimit\fP.
+
+This is a convenience wrapper interface around
+\fImemcpy\fP/\fIbyte_copy\fP to make it work like the other fmt
+functions.
+.SH "SEE ALSO"
+byte_copy(3), memcpy(3)

fmt/fmt_copybytes_sizeof_minus1.3

@@ -0,0 +1,26 @@
+.TH fmt_copybytes_sizeof_minus1 3
+.SH NAME
+fmt_copybytes_sizeof_minus1 \- write binary data
+.SH SYNTAX
+.B #include <libowfat/fmt.h>
+
+size_t \fBfmt_copybytes_sizeof_minus1\fP(char *\fIdest\fR,const char *\fIsource\fR);
+.SH DESCRIPTION
+This macro will copy sizeof(\fIsource\fP)-1 bytes from \fIsource\fP to \fIdest\fP.
+
+This is a convenience wrapper interface around
+\fIfmt_copybytes\fP for the situation where you construct a binary
+message by concatenating hex constant strings like this:
+
+  fmt_copybytes_sizeof_minus1(dest, "\\x01\\x02\\x03\\x04");
+
+Since the source is technically a string, the compiler will add a 0 byte
+and sizeof() will return the size including that 0 byte. That is why we
+have a minus 1 in this function, so we do not copy or count that 0 byte.
+
+.SH NOTE
+Caution: \fIsource\fP must not have side effects or those will be
+evaluated twice.
+
+.SH "SEE ALSO"
+fmt_copybytes(3)