Customizing C printf to print a fasta sequence

source.c

/**
* Author:
* 	Pierre Lindenbaum PhD
* Contact:
* 	plindenbaum@yahoo.fr
* Date:
*	2011-09-09
* WWW:
* 	http://plindenbaum.blogspot.com
* Reference:
* 	http://www.gnu.org/s/hello/manual/libc/Customizing-Printf.html
* Motivation:
* 	Customizing printf to print a fasta sequence
* Usage:
*	g++ -Wall source.c 
* 	./a.out < file.fasta
*/
#include <stdio.h>
#include <stdlib.h>
#include <printf.h>
#include <ctype.h>

typedef struct fasta_t
	{
	char* name;
	char* sequence;
	}Fasta;

#define FPUTC(C) ret+=(fputc(C,stream)==EOF?0:1)

/** handler for printf called by register_printf_function */
static int printf_fasta_handler(
	FILE *stream, /*  stream output */
	const struct printf_info *info, /* information about the various options */
         const void *const *args /* arguments */
	)
	{
	int n=0;
	int ret=0;
	char* p;
	/* return the number of character writtern */
	int lline =(info->prec<1?60:info->prec);
	const Fasta* fasta=*((const Fasta**)(args[0]));
	
	if(fasta->name!=NULL)
		{
		FPUTC('>');
		ret+=fputs(fasta->name,stream);
		}
	else
		{
		FPUTC('>');
		}
	
	if(fasta->sequence!=NULL)
		{
		p=(char*)fasta->sequence;
		while(p[n]!=0 && (info->width<1 || n< info->width))
			{
			if(n%lline==0) 
				{
				FPUTC('\n');
				}
			FPUTC(p[n]);
			++n;
			}
		}
	FPUTC('\n');
	return ret;
	}
static int printf_fasta_arginfo(
	const struct printf_info *info,
	size_t n,
	int *argtypes,
	int *size)
	{
	 /* We always take exactly one argument and this is a pointer to the
          structure.. */
	 if (n > 0) argtypes[0] = PA_POINTER;
	return 1;
	}

#define APPEND(ptr,len,c) {ptr=realloc(ptr,sizeof(char)*((len)+2));\
	if(ptr==NULL)\
		{\
		fputs("Out of memory\n",stderr);\
		exit(EXIT_FAILURE);\
		}\
	ptr[(len)]=c;\
	ptr[(len)+1]=0;\
	len++;\
	}
int main(int argc,char** argv)
	{
	size_t len_name=0;
	size_t len_seq=0;
	Fasta record;
	int c;
	
	/* register a new output conversion */
	if(register_printf_specifier('W',
		/* handler function */
		printf_fasta_handler,
		/* arginfo function */
		printf_fasta_arginfo 
		)!=0)
		{
		fputs("Cannot register print function",stderr);
		return EXIT_FAILURE;
		}
	record.name=NULL;
	record.sequence=NULL;
	for(;;)
		{
		c=fgetc(stdin);
		if(c==EOF || c=='>')
			{
			if(len_seq>0)
				{
				printf("%80W\n",&record);
				printf("%200.90W\n",&record);
				printf("%200W\n",&record);
				printf("%.80W\n",&record);
				}
			if(c==EOF) break;
			len_seq=0;
			len_name=0;
			while((c=fgetc(stdin))!=EOF && c!='\n')
				{
				APPEND(record.name,len_name,c);
				}
			}
		else if(!isspace(c))
			{
			APPEND(record.sequence,len_seq,c);
			}
		}
	free(record.name);
	free(record.sequence);
	return 0;
	}