1 files changed, 174 insertions, 0 deletions
diff --git a/src/http_next_header.c b/src/http_next_header.c
new file mode 100644
index 0000000..e2d2052
--- /dev/null
+++ b/src/http_next_header.c
@@ -0,0 +1,174 @@
+#include <ctype.h>
+#include <sqlite3.h>
+
+static int is_token_char(int c) {
+    return isalnum(c) || (c != 0 && strchr("!#$%&'*+-.^_`|~", c));
+}
+
+static int is_header_ws(int c) {
+    return c == ' ' || c == '\t';
+}
+
+static int is_vchar(int c) {
+    return c >= 0x21 && c <= 0x7e;
+}
+
+// Return SQLITE_ROW if a header was extracted
+// Return SQLITE_DONE if headers has been exhausted
+// Return SQLITE_ERROR on malformed input
+int http_next_header(const char* headers,
+                     int size,
+                     int* pParsed,
+                     const char** ppName,
+                     int* pNameSize,
+                     const char** ppValue,
+                     int* pValueSize) {
+    const char* headersEnd = headers + size;
+    const char* nameStart = NULL;
+    const char* nameEnd = NULL;
+    const char* valueStart = NULL;
+    const char* valueEnd = NULL;
+    const char* last = NULL;
+    const char* p = headers;
+
+    enum {
+        StateInit,
+        StateName,
+        StateNameTrailingWs,
+        StateValueLeadingWs,
+        StateValue,
+        StateCR,
+        StateCheckFold,
+        StateDone,
+        StateError,
+    };
+
+    int state = StateInit;
+
+    *ppName = NULL;
+    *pNameSize = 0;
+    *ppValue = NULL;
+    *pValueSize = 0;
+
+    if (size == 0) {
+        *pParsed = 0;
+        return SQLITE_DONE;
+    }
+
+    for (; p != headersEnd && state != StateDone && state != StateError; ++p) {
+        switch (state) {
+        case StateInit:
+            // printf("StateInit %02x %c\n", *p, isalnum(*p) ? *p : ' ');
+            if (*p == '\r') {
+                state = StateCR;
+            } else if (is_header_ws(*p)) {
+                // There shouldn't be whitespace here. Folding is handled in
+                // StateCR/StateCheckFold.
+                state = StateError;
+            } else {
+                nameStart = p;
+                state = StateName;
+            }
+            break;
+
+        case StateName:
+            // printf("StateName %02x %c\n", *p, isalnum(*p) ? *p : ' ');
+            if (is_token_char(*p)) {
+                // accept
+            } else if (*p == ':') {
+                nameEnd = p;
+                state = StateValueLeadingWs;
+            } else if (is_header_ws(*p)) {
+                nameEnd = p;
+                state = StateNameTrailingWs;
+            } else {
+                state = StateError;
+            }
+            break;
+
+        case StateNameTrailingWs:
+            // printf("StateNameTrailingWs %02x %c\n", *p, isalnum(*p) ? *p : ' ');
+            if (is_header_ws(*p)) {
+                // accept and skip
+            } else if (*p == ':') {
+                state = StateValueLeadingWs;
+            } else {
+                state = StateError;
+            }
+            break;
+
+        case StateValueLeadingWs:
+            // printf("StateValueLeadingWs %02x %c\n", *p, isalnum(*p) ? *p : ' ');
+            if (is_header_ws(*p)) {
+                // accept and skip
+            } else if (*p == '\r') {
+                // empty value
+                state = StateCR;
+            } else if (is_vchar(*p)) {
+                valueStart = p;
+                last = p;
+                state = StateValue;
+            } else {
+                state = StateError;
+            }
+            break;
+
+        case StateValue:
+            // printf("StateValue %02x %c\n", *p, isalnum(*p) ? *p : ' ');
+            if (is_header_ws(*p)) {
+                // accept but keep separate so that we can track trailing ws
+            } else if (*p == '\r') {
+                valueEnd = last + 1;
+                state = StateCR;
+            } else if (is_vchar(*p)) {
+                // accept
+                last = p;
+            }
+            break;
+
+        case StateCR:
+            // printf("StateCr %02x %c\n", *p, isalnum(*p) ? *p : ' ');
+            if (*p == '\n') {
+                // If there's more data, check for folding.
+                if (p + 1 == headers + size) {
+                    state = StateDone;
+                } else {
+                    state = StateCheckFold;
+                }
+            } else {
+                state = StateError;
+            }
+            break;
+
+        case StateCheckFold:
+            // printf("StateCheckFold %02x %c\n", *p, isalnum(*p) ? *p : ' ');
+            if (is_header_ws(*p)) {
+                state = StateValue;
+            } else {
+                state = StateDone;
+                --p;
+            }
+            break;
+        }
+    }
+
+    *pParsed = p - headers;
+
+    if (state != StateDone || state == StateError) {
+        return SQLITE_ERROR;
+    }
+
+    if (!nameStart) {
+        return SQLITE_DONE;
+    }
+
+    *ppName = nameStart;
+    *pNameSize = nameEnd - nameStart;
+
+    if (valueStart) {
+        *ppValue = valueStart;
+        *pValueSize = valueEnd - valueStart;
+    }
+
+    return SQLITE_ROW;
+}