tools: wc, head, and an argc/argv demo (args) + libc.c helpers

- c/libc.c: shared C helpers linked into every program - putu (print decimal),
  atou (parse decimal), argv_parse (tokenize getargs() into argc/argv).
- wc: count lines/words/chars of stdin. head [n]: first n lines (drains rest to
  EOF). args: argc/argv demo.
- pid now uses libc putu; build.sh links libc.c; Makefile CBLOBS + libc dep.
- README: document the new tools + argv_parse.
- verified: 'args one two three' -> argc=3/argv[..]; wc '2 3 16'; head 2.

1 files changed, 34 insertions, 0 deletions

diff --git a/c/libc.c b/c/libc.c
new file mode 100644
index 0000000..3b9883b
--- /dev/null
+++ b/c/libc.c
@@ -0,0 +1,34 @@
+/* gbos libc C helpers (compiled once, linked into every program). */
+#include "gbos.h"
+
+/* print an unsigned int in decimal */
+void putu(unsigned int n) {
+    char buf[5];
+    unsigned char i = 0;
+    if (n == 0) { putc('0'); return; }
+    while (n) { buf[i++] = '0' + (n % 10); n = n / 10; }
+    while (i) putc(buf[--i]);
+}
+
+/* parse a decimal number (stops at the first non-digit) */
+unsigned char atou(const char *s) {
+    unsigned char n = 0;
+    while (*s >= '0' && *s <= '9') { n = n * 10 + (*s - '0'); s++; }
+    return n;
+}
+
+/* tokenize the argument string in place into argv[]; returns argc.
+   (replaces the spaces in the arg string with NULs) */
+unsigned char argv_parse(char **argv, unsigned char maxv) {
+    char *p = getargs();
+    unsigned char argc = 0;
+    for (;;) {
+        while (*p == ' ') p++;
+        if (*p == 0) break;
+        if (argc < maxv) argv[argc] = p;
+        argc++;
+        while (*p != 0 && *p != ' ') p++;
+        if (*p == ' ') *p++ = 0;
+    }
+    return argc;
+}