3 files changed, 140 insertions, 0 deletions
diff --git a/core/cescal.c b/core/cescal.c
new file mode 100644
index 0000000..b9a2c17
--- /dev/null
+++ b/core/cescal.c
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include "cescal/state.h"
+
+static void
+help(void)
+{
+    printf("usage: ./cescal [flags]\n");
+    printf("[-h]    Display this help menu\n");
+}
+
+static int
+compile(const char *pathname)
+{
+    struct cescal_state st;
+
+    if (pathname == NULL) {
+        return -1;
+    }
+
+    if (state_init(&st, pathname) < 0) {
+        return -1;
+    }
+
+    state_close(&st);
+    return 0;
+}
+
+int
+main(int argc, char **argv)
+{
+    int opt;
+
+    if (argc < 2) {
+        printf("fatal: too few arguments\n");
+        help();
+        return -1;
+    }
+
+    while ((opt = getopt(argc, argv, "h")) != -1) {
+        switch (opt) {
+        case 'h':
+            help();
+            return -1;
+        }
+    }
+
+    while (optind < argc) {
+        if (compile(argv[optind++]) < 0) {
+            break;
+        }
+    }
+
+    return 0;
+}
diff --git a/core/readbuf.c b/core/readbuf.c
new file mode 100644
index 0000000..ee10362
--- /dev/null
+++ b/core/readbuf.c
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+#include <errno.h>
+#include <unistd.h>
+#include "cescal/readbuf.h"
+
+int
+readbuf_init(struct readbuf *rb)
+{
+    if (rb == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    rb->size = 0;
+    rb->tail = 0;
+    return 0;
+}
+
+char
+readbuf_read(struct readbuf *rb, int fd)
+{
+    ssize_t nread = -1;
+
+    if (rb == NULL || fd < 0) {
+        errno = EINVAL;
+        return '\0';
+    }
+
+#define N_RESIDUAL(rb) ((rb)->size - (rb)->tail)
+    if (N_RESIDUAL(rb) == 0 || rb->size == 0) {
+        if ((nread = read(fd, rb->buf, READBUF_CAP)) <= 0)
+            return nread;
+
+        rb->size = nread;
+        rb->tail = 0;
+    }
+#undef N_RESIDUAL
+
+    return rb->buf[rb->tail++];
+}
diff --git a/core/state.c b/core/state.c
new file mode 100644
index 0000000..7d80acd
--- /dev/null
+++ b/core/state.c
@@ -0,0 +1,34 @@
+#include <stdint.h>
+#include <stddef.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include "cescal/state.h"
+
+int
+state_init(struct cescal_state *state, const char *pathname)
+{
+    if (state == NULL || pathname == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    state->in_fd = open(pathname, O_RDONLY);
+    if (state->in_fd < 0) {
+        return -1;
+    }
+
+    if (readbuf_init(&state->rb) < 0) {
+        close(state->in_fd);
+        return -1;
+    }
+
+    return 0;
+}
+
+void
+state_close(struct cescal_state *state)
+{
+    close(state->in_fd);
+    state->in_fd = -1;
+}