code/inventory/scan.c

@@ -0,0 +1,94 @@
+/*
+ * scan.c - Phase 1 inventory demo: scan UPC barcodes and display them.
+ *
+ * Opens the barcode serial channel (TTY:D) and its own console/keyboard
+ * channel (CON:), then waits on both at once: a completed scan is validated
+ * as a UPC-A and printed; pressing Esc quits.
+ *
+ * Asynchronous two-channel wait (PLIB pattern): each request is started with
+ * p_ioc, which sets a status word to E_FILE_PENDING until the request
+ * completes. p_iowait blocks until some request finishes; we then check each
+ * status word, cancel the other outstanding request, and loop. Every started
+ * request is matched by exactly one completion (real or cancelled) so the I/O
+ * semaphore stays balanced. See "Asynchronous I/O" in the PLIB Reference.
+ */
+#include <plib.h>
+#include "bcode.h"
+#include "upc.h"
+
+#define KEY_ESC 27
+
+/*
+ * If a request on chan is still pending, cancel it and reap the resulting
+ * completion, so the started p_ioc is balanced by a wait.
+ */
+LOCAL_C VOID cancelPending(VOID *chan, WORD *pStat)
+{
+    if (*pStat == E_FILE_PENDING) {
+        p_iow(chan, P_FCANCEL);
+        p_waitstat(pStat);
+    }
+}
+
+GLDEF_C INT main(VOID)
+{
+    VOID *bchan;                /* barcode serial channel   */
+    VOID *kchan;                /* keyboard console channel */
+    WORD  bStat, kStat;         /* async status words       */
+    UBYTE bRaw[BCODE_MAXLEN];   /* raw bytes from one serial read */
+    UBYTE kRaw[1];              /* one keystroke                  */
+    TEXT  line[BCODE_MAXLEN];   /* barcode assembled across reads */
+    INT   lineLen = 0;
+    UWORD bLen, kLen;
+    INT   err;
+    INT   quit = 0;
+
+    if ((err = bcodeOpen(&bchan)) < 0) {
+        p_printf("Cannot open barcode port TTY:D (err %d)\n", err);
+        return 1;
+    }
+    if ((err = p_open(&kchan, "CON:", (UINT)-1)) < 0) {
+        p_printf("Cannot open console (err %d)\n", err);
+        bcodeClose(bchan);
+        return 1;
+    }
+
+    p_printf("Inventory scan demo\n");
+    p_printf("Scan a UPC, or press Esc to quit.\n\n");
+
+    while (quit == 0) {
+        /* Start one asynchronous read on each channel. */
+        bLen = sizeof(bRaw);
+        p_ioc(bchan, P_FREAD, &bStat, bRaw, &bLen);
+        kLen = sizeof(kRaw);
+        p_ioc(kchan, P_FREAD, &kStat, kRaw, &kLen);
+
+        p_iowait();
+
+        /* Keypress? Cancel the scan read and check for Esc. */
+        if (kStat != E_FILE_PENDING) {
+            cancelPending(bchan, &bStat);
+            if (kStat >= 0 && kRaw[0] == KEY_ESC)
+                quit = 1;
+            continue;
+        }
+
+        /* Scanner delivered bytes. Cancel the keypress read and assemble. */
+        if (bStat != E_FILE_PENDING) {
+            cancelPending(kchan, &kStat);
+            if (bStat >= 0 && bLen > 0) {
+                if (bcodeAssemble(bRaw, (INT)bLen, line, &lineLen, BCODE_MAXLEN)) {
+                    if (upcIsValid(line))
+                        p_printf("OK   %s\n", line);
+                    else
+                        p_printf("BAD  %s  (not a valid UPC-A)\n", line);
+                }
+            }
+        }
+    }
+
+    p_printf("\nDone.\n");
+    p_close(kchan);
+    bcodeClose(bchan);
+    return 0;
+}