Initial commit.

1 files changed, 216 insertions, 0 deletions

diff --git a/src/pdf_parser.c b/src/pdf_parser.c
new file mode 100644
index 0000000..1da8dff
--- /dev/null
+++ b/src/pdf_parser.c
@@ -0,0 +1,216 @@
+/*
+ * Copyright (c) 2020, yzrh <yzrh@tuta.io>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifdef __linux__
+
+#define _GNU_SOURCE
+
+#endif /* __linux__ */
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "pdf.h"
+
+static void *
+_memmem_whitespace(const void *p0, size_t s0, const void *p1, size_t s1)
+{
+	const char whitespace[6] = {
+		'\r',
+		'\n',
+		'\f',
+		'\t',
+		'\0',
+		' '
+	};
+
+	char tmp[s1 + 1];
+	memcpy(tmp, p1, s1);
+
+	char *ret;
+
+	for (int i = 0; i < 6; i++) {
+		tmp[s1] = whitespace[i];
+		if((ret = memmem(p0, s0, tmp, s1 + 1)) != NULL)
+			return ret;
+	}
+
+	return NULL;
+}
+
+static int
+_locate(pdf_object_t **pdf, FILE **fp, int size_buf)
+{
+	pdf_object_t *ptr = *pdf;
+	while (ptr->next != NULL)
+		ptr = ptr->next;
+
+	char buf[size_buf];
+
+	long cur = ftell(*fp);
+	long end;
+
+	fseek(*fp, 0, SEEK_END);
+	end = ftell(*fp);
+	fseek(*fp, cur, SEEK_SET);
+
+	int head = 0;
+	int tail = 0;
+	char *pos;
+	char *tmp;
+
+	for (;;) {
+		fread(buf, size_buf, 1, *fp);
+
+		if (head == 0 && (pos = _memmem_whitespace(buf, size_buf, " 0 obj", 6)) != NULL)
+			head = cur + (pos - buf) + 7;
+
+		if (tail == 0 && (pos = _memmem_whitespace(buf, size_buf, "endobj", 6)) != NULL) {
+			/* We need to check if it is the object stored in stream */
+			while (memcmp(pos + 7,
+				"\r\nendstream", 11) == 0 &&
+				(tmp = _memmem_whitespace(pos + 6,
+				size_buf - (pos - buf) - 6,
+				"endobj", 6)) != NULL)
+					pos = tmp;
+
+			if (pos - buf < size_buf - 7)
+				tail = cur + (pos - buf);
+		}
+
+		if (tail > head) {
+			if (ptr->next == NULL) {
+				ptr->next = malloc(sizeof(pdf_object_t));
+
+				if (ptr->next == NULL)
+					return 1;
+
+				ptr->next->id = 0;
+				ptr->next->object_size = 0;
+				ptr->next->object = NULL;
+				ptr->next->dictionary_size = 0;
+				ptr->next->dictionary = NULL;
+				ptr->next->stream_size = 0;
+				ptr->next->stream = NULL;
+				ptr->next->next = NULL;
+				ptr = ptr->next;
+			}
+
+			ptr->address = head;
+			ptr->size = tail - head;
+
+			fseek(*fp, tail + 6, SEEK_SET);
+			head = tail = 0;
+		} else {
+			fseek(*fp, -6, SEEK_CUR);
+		}
+
+		if ((cur = ftell(*fp)) + 6 >= end)
+			break;
+	}
+
+	return 0;
+}
+
+int
+pdf_load(pdf_object_t **pdf, FILE **fp, int size_buf)
+{
+	if (*pdf == NULL || *fp == NULL || size_buf < 7)
+		return 1;
+
+	if (_locate(pdf, fp, size_buf) != 0)
+		return 1;
+
+	pdf_object_t *ptr = (*pdf)->next;
+
+	char *buf;
+	char *head;
+	char *tail;
+	char *tmp;
+
+	while (ptr != NULL) {
+		buf = malloc(ptr->size);
+
+		if (buf == NULL)
+			return 1;
+
+		memset(buf, 0, ptr->size);
+
+		fseek(*fp, ptr->address - 12, SEEK_SET);
+		fread(buf, 8, 1, *fp);
+
+		for (int i = 0; i < 8; i++) {
+			if (buf[i] >= '0' && buf[i] <= '9') {
+				ptr->id = atoi(buf + i);
+				break;
+			}
+		}
+
+		fseek(*fp, ptr->address, SEEK_SET);
+		fread(buf, ptr->size, 1, *fp);
+
+		if ((head = memmem(buf, ptr->size, "<<", 2)) != NULL &&
+			(tail = _memmem_whitespace(buf, ptr->size, ">>", 2)) != NULL) {
+			/* A dictionary object may have nested dictionary */
+			while ((tmp = _memmem_whitespace(tail + 2,
+				ptr->size - (tail - buf) - 2,
+				">>", 2)) != NULL)
+				tail = tmp;
+
+			ptr->dictionary_size = tail - head + 2;
+			ptr->dictionary = malloc(ptr->dictionary_size + 1);
+
+			if (ptr->dictionary == NULL)
+				return 1;
+
+			memset(ptr->dictionary, 0, ptr->dictionary_size + 1);
+			memcpy(ptr->dictionary, head, ptr->dictionary_size);
+
+			if ((head = memmem(tail,
+				ptr->size - (tail - buf),
+				"stream\r\n", 8)) != NULL &&
+				(tail = _memmem_whitespace(head,
+				ptr->size - (head - buf),
+				"endstream", 9)) != NULL) {
+				/*
+				 * An object may contain a stream that
+				 * contains another object that
+				 * contains another stream
+				 */
+				while (_memmem_whitespace(tail,
+					ptr->size - (tail - buf),
+					"endobj", 6) != NULL &&
+					(tmp = _memmem_whitespace(tail + 9,
+					ptr->size - (tail - buf) - 9,
+					"endstream", 9)) != NULL)
+						tail = tmp;
+
+				ptr->stream_size = (tail - head) - 8;
+				ptr->stream = malloc(ptr->stream_size);
+
+				if (ptr->stream == NULL)
+					return 1;
+
+				memcpy(ptr->stream, head + 8, ptr->stream_size);
+			}
+		} else {
+			ptr->object_size = ptr->size;
+			ptr->object = malloc(ptr->object_size + 1);
+
+			if (ptr->object == NULL)
+				return 1;
+
+			memset(ptr->object, 0, ptr->object_size + 1);
+			memcpy(ptr->object, buf, ptr->object_size);
+		}
+
+		free(buf);
+
+		ptr = ptr->next;
+	}
+
+	return 0;
+}