feat: add streq and printErr

user/fiforeader.c

@@ -0,0 +1,53 @@
+#include "ulib.h"
+
+/*
+ * Only ever spawned by fifomaster.c, with the shared pipe's handle number
+ * as argv[1]. Attaches its end and immediately calls a blocking read() on
+ * a pipe fifowriter.c (spawned alongside it, sleeping before it writes)
+ * has not put anything into yet -- this call must genuinely park (the
+ * syscall-restart path in syscall.c's sysRead, parked on pipeChannel) and
+ * only return once fifowriter.c's write wakes it back up, not before.
+ */
+
+static int streq(const char* a, const char* b)
+{
+    while (*a && *a == *b) {
+        a++;
+        b++;
+    }
+    return *a == *b;
+}
+
+int main(int argc, char** argv)
+{
+    if (argc != 2) {
+        print("fiforeader: FAIL expected one argv (pipe handle)\n");
+        return 1;
+    }
+
+    long handle = parseDec(argv[1]);
+    long fd = userPipeAttach(handle, 0);
+    if (fd < 0) {
+        print("fiforeader: FAIL attach\n");
+        return 1;
+    }
+
+    print("fiforeader: attached, blocking on read\n");
+    char buffer[64];
+    long got = userRead((int)fd, buffer, sizeof(buffer) - 1);
+    if (got <= 0) {
+        print("fiforeader: FAIL read\n");
+        return 1;
+    }
+    buffer[got] = 0;
+
+    print("fiforeader: got: ");
+    print(buffer);
+    print("\n");
+
+    int ok = streq(buffer, "shared pipe payload");
+    print(ok ? "fiforeader: payload-ok\n" : "fiforeader: payload-FAIL\n");
+
+    userClose((int)fd);
+    return ok ? 0 : 1;
+}