1 files changed, 115 insertions, 0 deletions
diff --git a/research/experiments/044-specs/json_check.py b/research/experiments/044-specs/json_check.py
new file mode 100644
index 0000000..b5d62f0
--- /dev/null
+++ b/research/experiments/044-specs/json_check.py
@@ -0,0 +1,115 @@
+# Whether bytes are one JSON text (RFC 8259): the design of aup's examples/json.aup in plain Python, the reference
+# 140 counts its lines against (read once from the start, a stack of the arrays and objects open).
+def space(b):
+    return b in (0x20, 0x09, 0x0a, 0x0d)
+
+
+def digit(b):
+    return 0x30 <= b <= 0x39
+
+
+def hexdigit(b):
+    return digit(b) or 0x61 <= b <= 0x66 or 0x41 <= b <= 0x46
+
+
+def valid(d):
+    try:
+        t = d.decode('utf-8')
+    except UnicodeDecodeError:
+        return False
+    n, i, mode, ok, open_ = len(d), 0, 0, True, []  # mode 0: a value, 1: after one, 2: a key, 3: a key or }, 4: a value or ]
+    while ok:
+        while i < n and space(d[i]):
+            i += 1
+        if i == n:
+            return mode == 1 and not open_
+        b = d[i]
+        if mode == 1:
+            if not open_:
+                ok = False
+            elif b == 0x2c:
+                mode = 0 if open_[-1] == 0x5b else 2
+            elif b == open_[-1] + 2:
+                open_.pop()
+            else:
+                ok = False
+            i += 1
+        elif mode == 3 and b == 0x7d or mode == 4 and b == 0x5d:
+            open_.pop()
+            mode = 1
+            i += 1
+        elif mode in (2, 3):
+            ok = b == 0x22
+            mode = 5
+        elif b in (0x5b, 0x7b):
+            open_.append(b)
+            mode = 4 if b == 0x5b else 3
+            i += 1
+        elif b == 0x22 or mode == 5:
+            i += 1
+            while i < n and d[i] != 0x22 and ok:
+                if d[i] < 0x20:
+                    ok = False
+                elif d[i] == 0x5c and i + 1 < n and d[i + 1] == 0x75:
+                    ok = i + 5 < n and all(hexdigit(x) for x in d[i + 2:i + 6])
+                    i += 6
+                elif d[i] == 0x5c:
+                    ok = i + 1 < n and d[i + 1] in b'"\\/bfnrt'
+                    i += 2
+                else:
+                    i += 1
+            ok = ok and i < n
+            i += 1
+            if mode == 5:
+                while i < n and space(d[i]):
+                    i += 1
+                ok = ok and i < n and d[i] == 0x3a
+                i += 1
+                mode = 0
+            else:
+                mode = 1
+        elif b == 0x2d or digit(b):
+            if b == 0x2d:
+                i += 1
+            ok = i < n and digit(d[i])
+            if ok and d[i] == 0x30:
+                i += 1
+            else:
+                while i < n and digit(d[i]):
+                    i += 1
+            if ok and i < n and d[i] == 0x2e:
+                i += 1
+                ok = i < n and digit(d[i])
+                while i < n and digit(d[i]):
+                    i += 1
+            if ok and i < n and d[i] in (0x65, 0x45):
+                i += 1
+                if i < n and d[i] in (0x2b, 0x2d):
+                    i += 1
+                ok = i < n and digit(d[i])
+                while i < n and digit(d[i]):
+                    i += 1
+            mode = 1
+        else:
+            word = b'true' if b == 0x74 else b'false' if b == 0x66 else b'null'
+            ok = d[i:i + len(word)] == word
+            i += len(word)
+            mode = 1
+    return False
+
+
+if __name__ == '__main__':
+    import os, sys, time
+    suite = sys.argv[1]
+    files = sorted(os.listdir(suite))
+    data = [open(os.path.join(suite, f), 'rb').read() for f in files]
+    for f, d in zip(files, data):
+        assert not f.startswith('y_') or valid(d), f
+        assert not f.startswith('n_') or not valid(d), f
+    big = b'[' + b','.join(b'{"key%d": [1.5e3, true, null, "text \\u00e9 %d"]}' % (k, k) for k in range(2000)) + b']'
+    runs = []
+    for _ in range(7):
+        start = time.perf_counter()
+        valid(big)
+        runs.append((time.perf_counter() - start) * 1e9 / len(big))
+    print('{"size":%d,"python_ns_per_byte":%.1f}' % (len(big), sorted(runs)[3]))