split: let me join bikeshed painting frenzy :)

this one should be able to handle huge files.
   text    data     bss     dec     hex filename
    664       4       0     668     29c busybox.t0/coreutils/split.o
    628       0       0     628     274 busybox.t1/coreutils/split.o
split_main                                           488     525     +37
suffix_len                                             4       -      -4
next_file                                             77       -     -77
(add/remove: 0/2 grow/shrink: 1/0 up/down: 37/-81)            Total: -44 bytes

1 files changed, 71 insertions, 68 deletions

diff --git a/coreutils/split.c b/coreutils/split.c
index ca546986e..07eb97e0c 100644
--- a/coreutils/split.c
+++ b/coreutils/split.c
@@ -10,44 +10,43 @@
  * http://www.opengroup.org/onlinepubs/009695399/utilities/split.html
  */
 #include "busybox.h"
-static unsigned suffix_len = 2;
+
 static const struct suffix_mult split_suffices[] = {
-#if ENABLE_FEATURE_SPLIT_FANCY
         { "b", 512 },
-#endif
         { "k", 1024 },
         { "m", 1024*1024 },
-#if ENABLE_FEATURE_SPLIT_FANCY
         { "g", 1024*1024*1024 },
-#endif
         { NULL, 0 }
 };
 
 /* Increment the suffix part of the filename.
- * Returns 0 on success and 1 on error (if we are out of files)
+ * Returns NULL if we are out of filenames.
  */
-static bool next_file(char **old)
+static char *next_file(char *old, unsigned suffix_len)
 {
-        size_t end = strlen(*old);
+        size_t end = strlen(old);
         unsigned i = 1;
         char *curr;
 
         do {
-                curr = *old + end - i;
+                curr = old + end - i;
                 if (*curr < 'z') {
                         *curr += 1;
                         break;
                 }
                 i++;
                 if (i > suffix_len) {
-                        bb_error_msg("Suffices exhausted");
-                        return 1;
+                        return NULL;
                 }
                 *curr = 'a';
         } while (1);
-        return 0;
+
+        return old;
 }
 
+#define read_buffer bb_common_bufsiz1
+enum { READ_BUFFER_SIZE = sizeof(bb_common_bufsiz1) - 1 };
+
 #define SPLIT_OPT_l (1<<0)
 #define SPLIT_OPT_b (1<<1)
 #define SPLIT_OPT_a (1<<2)
@@ -55,79 +54,83 @@ static bool next_file(char **old)
 int split_main(int argc, char **argv);
 int split_main(int argc, char **argv)
 {
-        char *pfx, *buf, *input_file;
-        unsigned cnt = 1000, opt;
-        bool ret = EXIT_SUCCESS;
-        FILE *fp;
-        char *count_p, *sfx;
-//XXX: FIXME    opt_complementary = "+2"; /* at most 2 non-option arguments */
+        unsigned suffix_len = 2;
+        char *pfx;
+        char *count_p;
+        const char *sfx;
+        unsigned long cnt = 1000;
+        unsigned long remaining = 0;
+        unsigned opt;
+        int bytes_read, to_write;
+        char *src;
+
+        opt_complementary = "?2";
         opt = getopt32(argc, argv, "l:b:a:", &count_p, &count_p, &sfx);
 
         if (opt & SPLIT_OPT_l)
-                cnt = xatoi(count_p);
+                cnt = xatoul(count_p);
         if (opt & SPLIT_OPT_b)
                 cnt = xatoul_sfx(count_p, split_suffices);
         if (opt & SPLIT_OPT_a)
-                suffix_len = xatoi(sfx);
+                suffix_len = xatou(sfx);
         argv += optind;
-        if (!*argv)
-                *--argv = (char*) "-";
-        input_file = *argv;
-        sfx = *++argv;
+        sfx = "x";
+        if (argv[0]) {
+                if (argv[1])
+                        sfx = argv[1];
+                xmove_fd(xopen(argv[0], O_RDONLY), 0);
+        } else {
+                argv[0] = (char *) bb_msg_standard_input;
+        }
 
-        if (sfx && (NAME_MAX < strlen(sfx) + suffix_len))
-                        bb_error_msg_and_die("Suffix too long");
+        if (NAME_MAX < strlen(sfx) + suffix_len)
+                bb_error_msg_and_die("suffix too long");
 
         {
-                char *char_p = xzalloc(suffix_len);
+                char *char_p = xzalloc(suffix_len + 1);
                 memset(char_p, 'a', suffix_len);
-                pfx = xasprintf("%s%s", sfx ? sfx : "x", char_p);
+                pfx = xasprintf("%s%s", sfx, char_p);
                 if (ENABLE_FEATURE_CLEAN_UP)
                         free(char_p);
         }
-        fp = fopen_or_warn_stdin(input_file);
-//XXX:FIXME: unify those two file-handling schemata below (FILE vs fd) !
-        if (opt & SPLIT_OPT_b) {
-                ssize_t i;
-                ssize_t bytes = 0;
-                int inp = fileno(fp);
 
+        while (1) {
+                bytes_read = safe_read(0, read_buffer, READ_BUFFER_SIZE);
+                if (!bytes_read)
+                        break;
+                if (bytes_read < 0)
+                        bb_perror_msg_and_die("%s", argv[0]);
+                src = read_buffer;
                 do {
-                        int out = xopen(pfx, O_WRONLY | O_CREAT | O_TRUNC);
-                        lseek(inp, bytes, SEEK_SET);
-                        buf = xzalloc(cnt);
-                        bytes += i = full_read(inp, buf, cnt);
-                        xwrite(out, buf, i);
-                        free(buf);
-                        close(out);
-                        if (next_file(&pfx)) {
-                                ret++;
-                                goto bail;
+                        if (!remaining) {
+                                if (!pfx)
+                                        bb_error_msg_and_die("suffices exhausted");
+                                xmove_fd(xopen(pfx, O_WRONLY | O_CREAT | O_TRUNC), 1);
+                                pfx = next_file(pfx, suffix_len);
+                                remaining = cnt;
                         }
-                } while (i == cnt); /* if we read less than cnt, then nothing is left */
-        } else { /* -l */
-                do {
-                        unsigned i = cnt;
-                        int out = xopen(pfx, O_WRONLY | O_CREAT | O_TRUNC);
-                        buf = NULL;
-                        while (i--) {
-                            buf = xmalloc_fgets(fp);
-                                if (buf == NULL)
-                                        break;
-                                xwrite(out, buf, strlen(buf));
-                                free(buf);
-                        };
-                        close(out);
-                        if (next_file(&pfx)) {
-                                ret++;
-                                goto bail;
+
+                        if (opt & SPLIT_OPT_b) {
+                                /* split by bytes */
+                                to_write = (bytes_read < remaining) ? bytes_read : remaining;
+                                remaining -= to_write;
+                        } else {
+                                /* split by lines */
+                                /* can be sped up by using _memrchr_
+                                 * and writing many lines at once... */
+                                char *end = memchr(src, '\n', bytes_read);
+                                if (end) {
+                                        --remaining;
+                                        to_write = end - src + 1;
+                                } else {
+                                        to_write = bytes_read;
+                                }
                         }
-                } while (buf);
-        }
-bail:
-        if (ENABLE_FEATURE_CLEAN_UP) {
-                free(pfx);
-                fclose_if_not_stdin(fp);
+
+                        xwrite(1, src, to_write);
+                        bytes_read -= to_write;
+                        src += to_write;
+                } while (bytes_read);
         }
-        return ret;
+        return 0;
 }