first commit

.gitignore

@@ -0,0 +1,2 @@
+b64
+*.o

Makefile

@@ -0,0 +1,13 @@
+CFLAGS = -g -Wall -Wextra -Werror
+
+objects = main.o input.o trans.o
+
+b64 : $(objects)
+	cc -o b64 $(objects)
+
+main.o trans.o input.o : input.h
+main.o trans.o : trans.h
+
+.PHONY : clean
+clean :
+	rm -f b64 $(objects)

input.c

@@ -0,0 +1,37 @@
+#include "input.h"
+
+#define OBUFSIZE  4
+#define SBUFSIZE  5
+
+#define PADDING '='
+
+unsigned char o[OBUFSIZE];
+unsigned char s[SBUFSIZE];
+
+unsigned char *
+getocts(FILE *fp, int *np)
+{
+    int n, c;
+
+    n = 0;
+    while (n < OBUFSIZE-1 && (c = fgetc(fp)) != EOF)
+        o[n++] = c;
+    *np = n;
+
+    return (*np) ? o : NULL;
+}
+
+unsigned char *
+getsxts(FILE *fp, int *np)
+{
+    int n, p, c;
+
+    n = p = 0;
+    while (n < SBUFSIZE-1 && (c = fgetc(fp)) != EOF && c != PADDING)
+        s[n++] = c;
+    while (n+p < SBUFSIZE-1)
+        s[n+p++] = PADDING;
+    *np = n;
+
+    return (n) ? s : NULL;
+}

input.h

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+#ifndef HEADER_INPUT
+#define HEADER_INPUT
+
+#include <stdio.h>
+
+extern unsigned char o[];
+extern unsigned char s[];
+
+unsigned char *
+getocts(FILE *fp, int *np);
+
+unsigned char *
+getsxts(FILE *fp, int *np);
+
+#endif

main.c

@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "input.h"
+#include "trans.h"
+
+int
+main(int argc, char *argv[])
+{
+    int c, n, dec, hlp;
+    char *prog = *argv;
+    unsigned char *b;
+    FILE *fp;
+
+    dec = hlp = 0;
+    while (--argc > 0 && (*++argv)[0] == '-')
+        while ((c = *++argv[0]))
+            switch (c) {
+                case 'd':
+                    dec = 1;
+                    break;
+                case 'h':
+                    hlp = 1;
+                    break;
+                default:
+                    fprintf(stderr, "%s: illegal option %c\n", prog, c);
+                    exit(EXIT_FAILURE);
+                    break;
+            }
+    if (hlp) {
+        fprintf(stdout, "Usage: %s -d -h file\n", prog);
+    } else if (argc != 1) {
+        if (dec) {
+            while ((b = getsxts(stdin, &n))) {
+                    b = decode(b, &n);
+                    fwrite(b, sizeof(*b), n, stdout);
+            }
+        } else {
+            while ((b = getocts(stdin, &n)))
+                    printf("%s", encode(b, n));
+        }
+    } else {
+        if ((fp = fopen(*argv, "r")) == NULL) {
+            fprintf(stderr, "%s: can't open %s\n", prog, *argv);
+            exit(EXIT_FAILURE);
+        }
+        else if (dec) {
+            while ((b = getsxts(fp, &n))) {
+                    b = decode(b, &n);
+                    fwrite(b, sizeof(*b), n, stdout);
+            }
+        } else {
+            while ((b = getocts(fp, &n)))
+                    printf("%s", encode(b, n));
+        }
+        fclose(fp);
+    }
+    exit(EXIT_SUCCESS);
+}

trans.c

@@ -0,0 +1,97 @@
+#include "trans.h"
+
+#define PADDING '='
+
+unsigned char b64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
+                      "abcdefghijklmnopqrstuvwxyz" \
+                      "0123456789" \
+                      "+/";
+
+unsigned char *
+encode(unsigned char *op, int np)
+{
+    extern unsigned char s[];
+    unsigned char *sp;
+    int n;
+
+    sp = s;
+    switch (np) {
+        case 3:
+            *sp++ = b64[(*op & ~3) >> 2];
+            n = (*op++ & 3) << 4;
+            *sp++ = b64[n + ((*op & ~15) >> 4)];
+            n = (*op++ & 15) << 2;
+            *sp++ = b64[n + ((*op & 192) >> 6)];
+            *sp = b64[*op & ~192];
+            break;
+        case 2:
+            *sp++ = b64[(*op & ~3) >> 2];
+            n = (*op++ & 3) << 4;
+            *sp++ = b64[n + ((*op & ~15) >> 4)];
+            *sp++ = b64[(*op & 15) << 2];
+            *sp = PADDING;
+            break;
+        case 1:
+            *sp++ = b64[(*op & ~3) >> 2];
+            *sp++ = b64[(*op & 3) << 4];
+            *sp++ = PADDING;
+            *sp = PADDING;
+            break;
+    }
+
+    return s;
+}
+
+unsigned char *
+decode(unsigned char *sp, int *np)
+{
+    extern unsigned char o[];
+    unsigned char *op;
+    int n, b, atob(int c);
+
+    op = o;
+    switch (*np) {
+        case 4:
+            n = atob(*sp++) << 2;
+            b = atob(*sp++);
+            *op++ = n + ((b & ~15) >> 4);
+
+            n = (b & 15) << 4;
+            b = atob(*sp++);
+            *op++ = n + ((b & ~3) >> 2);
+
+            *op = ((b & 3) << 6) + atob(*sp);
+            break;
+        case 3:
+            n = atob(*sp++) << 2;
+            b = atob(*sp++);
+            *op++ = n + ((b & ~15) >> 4);
+
+            n = (b & 15) << 4;
+            *op = n + ((atob(*sp) & ~3) >> 2);
+            break;
+        case 2:
+            n = atob(*sp++) << 2;
+            *op = n + ((atob(*sp) & ~15) >> 4);
+            break;
+    }
+    *np = op-o+1;
+
+    return o;
+}
+
+int atob(int c)
+{
+    if (c >= 'A' && c <= 'Z')
+        c -= 'A';
+    else if (c >= 'a' && c <= 'z')
+        c = c - 'a' + 26;
+    else if (c >= '0' && c <= '9')
+        c = c - '0' + 26 * 2;
+    else if (c == '+')
+        c = 62;
+    else
+        c = 63;
+
+    return c;
+}

trans.h

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+#ifndef HEADER_TRANS
+#define HEADER_TRANS
+
+#include "input.h"
+
+unsigned char *
+encode(unsigned char *op, int np);
+
+unsigned char *
+decode(unsigned char *sp, int *np);
+
+#endif