1 files changed, 147 insertions, 0 deletions
diff --git a/src/section/export.c b/src/section/export.c
new file mode 100644
index 0000000..9ca8de5
--- /dev/null
+++ b/src/section/export.c
@@ -0,0 +1,147 @@
+#include <sections.h>
+#include <wasm_types.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+static int check_string(FILE *const f)
+{
+    varuint32 len;
+
+    if (varuint32_read(f, &len))
+    {
+        fprintf(stderr, "%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < len; i++)
+    {
+        uint8_t byte;
+
+        if (!fread(&byte, sizeof byte, 1, f))
+        {
+            fprintf(stderr, "%s: fread(3) failed, feof=%d, ferror=%d\n",
+                __func__, feof(f), ferror(f));
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static int check_kind(FILE *const f)
+{
+    varuint32 type;
+
+    if (varuint32_read(f, &type))
+    {
+        fprintf(stderr, "%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check_index(FILE *const f)
+{
+    varuint32 index;
+
+    if (varuint32_read(f, &index))
+    {
+        fprintf(stderr, "%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check_export_entry(FILE *const f)
+{
+    if (check_string(f))
+    {
+        fprintf(stderr, "%s: check_string failed\n", __func__);
+        return -1;
+    }
+    else if (check_kind(f))
+    {
+        fprintf(stderr, "%s: check_kind failed\n", __func__);
+        return -1;
+    }
+    else if (check_index(f))
+    {
+        fprintf(stderr, "%s: check_index failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check(FILE *const f, const unsigned long len)
+{
+    const long start = ftell(f);
+    varuint32 count;
+
+    if (start < 0)
+    {
+        fprintf(stderr, "%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (varuint32_read(f, &count))
+    {
+        fprintf(stderr, "%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < count; i++)
+        if (check_export_entry(f))
+        {
+            fprintf(stderr, "%s: check_export_entry failed\n", __func__);
+            return -1;
+        }
+
+    const long end = ftell(f);
+
+    if (end < 0)
+    {
+        fprintf(stderr, "%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const unsigned long size = end - start;
+
+    if (size != len)
+    {
+        fprintf(stderr, "%s: size exceeded (%lu expected, got %lu)\n",
+                __func__, len, size);
+        return -1;
+    }
+
+    return 0;
+}
+
+int section_export(struct wasmfs *const w, FILE *const f,
+    const unsigned long len)
+{
+    if (w->sections.export)
+    {
+        fprintf(stderr, "%s: ignoring duplicate section\n", __func__);
+        return 0;
+    }
+
+    const long offset = ftell(f);
+
+    if (offset < 0)
+    {
+        fprintf(stderr, "%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (check(f, len))
+    {
+        fprintf(stderr, "%s: check failed\n", __func__);
+        return -1;
+    }
+
+    w->sections.export = offset;
+    return 0;
+}