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I recently found, The Practice of Programming (Addison-Wesley Professional Computing Series), sitting on the shelf at my local library. I am generally skeptical when it comes to programming books, and particularly those from different decades, but I trusted the name "Brian Kernighan" so I checked the book out.
And I am so glad that I did. From the first chapter that discussed style, I wanted to read more. And the only reason to ever stop reading was to pull out a computer and put these things into practice. I didn't even mind that it wasn't until chapter 7 that performance was discussed. Still, I will readily acknowledge that I disagree with some of statements in the book. Furthermore, there are some parts of the text that are clearly dated, like discussing current C / C++ standards.
I'd like to conclude with a brief code snippet from the work. This code is part of a serializer / deserializer. Such routines are always a pain to write and particularly if you have many different classes / structs that need them. Thus the authors suggest using vargs and writing a single routine that can handle this for you. Here is the unpack (i.e., deserialize) routine:
/* unpack: unpack packed items from buf, return length */
int unpack(uchar *buf, char *fmt, ...)
{
va_list args;
char *p;
uchar *bp, *pc;
ushort *ps;
ulong *pl;
bp = buf;
va_start(args, fmt);
for (p = fmt; *p != '\0'; p++) {
switch (*p) {
case 'c': /* char */
pc = va_arg(args, uchar*);
*pc = *bp++;
break;
case 's': /* short */
ps = va_arg(args, ushort*);
*ps = *bp++ << 8;
*ps |= *bp++;
break;
case 'l': /* long */
pl = va_arg(args, ulong*);
*pl = *bp++ << 24;
*pl |= *bp++ << 16;
*pl |= *bp++ << 8;
*pl |= *bp++;
default: /* illegal type character */
va_end(args);
return -1;
}
}
va_end(args);
return bp - buf;
}
So now we have a little language for describing the format of the data in the buffer. We invoke unpack with a string like "cscl" and pointers to store the char, short, char and long. Hah! That's it. Anytime we add new types, we just to call the pack / unpack.
Does it matter that the variables are only sequences like "pl" or "bp"? No. Variable names should be meaningful and consistent. "i" can be fine for a loop iterator.
We have given up some performance (*gasp*), but gained in the other parts that matter like readability and maintainability. I plan on using this in my current research (but only the unpack, as my serializers are already highly optimized). All in all, I approve of this book and may even someday require it as a textbook for students.
