Add internal Pl_Base64

Bidirectional base64; will be used by JSON v2.

3 files changed, 222 insertions, 0 deletions

diff --git a/libqpdf/CMakeLists.txt b/libqpdf/CMakeLists.txt
index 305977de..72b87975 100644
--- a/libqpdf/CMakeLists.txt
+++ b/libqpdf/CMakeLists.txt
@@ -35,6 +35,7 @@ set(libqpdf_SOURCES
   Pl_AES_PDF.cc
   Pl_ASCII85Decoder.cc
   Pl_ASCIIHexDecoder.cc
+  Pl_Base64.cc
   Pl_Buffer.cc
   Pl_Concatenate.cc
   Pl_Count.cc
diff --git a/libqpdf/Pl_Base64.cc b/libqpdf/Pl_Base64.cc
new file mode 100644
index 00000000..bfacc1db
--- /dev/null
+++ b/libqpdf/Pl_Base64.cc
@@ -0,0 +1,191 @@
+#include <qpdf/Pl_Base64.hh>
+
+#include <qpdf/QIntC.hh>
+#include <qpdf/QUtil.hh>
+#include <algorithm>
+#include <cstring>
+#include <stdexcept>
+
+static char
+to_c(unsigned int ch)
+{
+    return static_cast<char>(ch);
+}
+
+static unsigned char
+to_uc(int ch)
+{
+    return static_cast<unsigned char>(ch);
+}
+
+static int
+to_i(int i)
+{
+    return static_cast<int>(i);
+}
+
+Pl_Base64::Pl_Base64(char const* identifier, Pipeline* next, action_e action) :
+    Pipeline(identifier, next),
+    action(action),
+    pos(0),
+    end_of_data(false),
+    finished(false)
+{
+    reset();
+}
+
+void
+Pl_Base64::write(unsigned char* data, size_t len)
+{
+    if (finished) {
+        throw std::logic_error("Pl_Base64 used after finished");
+    }
+    if (this->action == a_decode) {
+        decode(data, len);
+    } else {
+        encode(data, len);
+    }
+}
+
+void
+Pl_Base64::decode(unsigned char* data, size_t len)
+{
+    unsigned char* p = data;
+    while (len > 0) {
+        if (!QUtil::is_space(to_c(*p))) {
+            this->buf[this->pos++] = *p;
+            if (this->pos == 4) {
+                flush();
+            }
+        }
+        ++p;
+        --len;
+    }
+}
+
+void
+Pl_Base64::encode(unsigned char* data, size_t len)
+{
+    unsigned char* p = data;
+    while (len > 0) {
+        this->buf[this->pos++] = *p;
+        if (this->pos == 3) {
+            flush();
+        }
+        ++p;
+        --len;
+    }
+}
+
+void
+Pl_Base64::flush()
+{
+    if (this->action == a_decode) {
+        flush_decode();
+    } else {
+        flush_encode();
+    }
+    reset();
+}
+
+void
+Pl_Base64::flush_decode()
+{
+    if (this->end_of_data) {
+        throw std::runtime_error(
+            getIdentifier() + ": base64 decode: data follows pad characters");
+    }
+    int pad = 0;
+    int shift = 18;
+    int outval = 0;
+    for (size_t i = 0; i < 4; ++i) {
+        int v = 0;
+        char ch = to_c(this->buf[i]);
+        if ((ch >= 'A') && (ch <= 'Z')) {
+            v = ch - 'A';
+        } else if ((ch >= 'a') && (ch <= 'z')) {
+            v = ch - 'a' + 26;
+        } else if ((ch >= '0') && (ch <= '9')) {
+            v = ch - '0' + 52;
+        } else if ((ch == '+') || (ch == '-')) {
+            v = 62;
+        } else if ((ch == '/') || (ch == '_')) {
+            v = 63;
+        } else if (
+            (ch == '=') && ((i == 3) || ((i == 2) && (this->buf[3] == '=')))) {
+            ++pad;
+            this->end_of_data = true;
+            v = 0;
+        } else {
+            throw std::runtime_error(
+                getIdentifier() + ": base64 decode: invalid input");
+        }
+        outval |= v << shift;
+        shift -= 6;
+    }
+    unsigned char out[3] = {
+        to_uc(outval >> 16),
+        to_uc(0xff & (outval >> 8)),
+        to_uc(0xff & outval),
+    };
+
+    getNext()->write(out, QIntC::to_size(3 - pad));
+}
+
+void
+Pl_Base64::flush_encode()
+{
+    int outval = ((this->buf[0] << 16) | (this->buf[1] << 8) | (this->buf[2]));
+    unsigned char out[4] = {
+        to_uc(outval >> 18),
+        to_uc(0x3f & (outval >> 12)),
+        to_uc(0x3f & (outval >> 6)),
+        to_uc(0x3f & outval),
+    };
+    for (size_t i = 0; i < 4; ++i) {
+        int ch = to_i(out[i]);
+        if (ch < 26) {
+            ch += 'A';
+        } else if (ch < 52) {
+            ch -= 26;
+            ch += 'a';
+        } else if (ch < 62) {
+            ch -= 52;
+            ch += '0';
+        } else if (ch == 62) {
+            ch = '+';
+        } else if (ch == 63) {
+            ch = '/';
+        }
+        out[i] = to_uc(ch);
+    }
+    for (size_t i = 0; i < 3 - this->pos; ++i) {
+        out[3 - i] = '=';
+    }
+    getNext()->write(out, 4);
+}
+
+void
+Pl_Base64::finish()
+{
+    if (this->pos > 0) {
+        if (finished) {
+            throw std::logic_error("Pl_Base64 used after finished");
+        }
+        if (this->action == a_decode) {
+            for (size_t i = this->pos; i < 4; ++i) {
+                this->buf[i] = '=';
+            }
+        }
+        flush();
+    }
+    this->finished = true;
+    getNext()->finish();
+}
+
+void
+Pl_Base64::reset()
+{
+    this->pos = 0;
+    memset(buf, 0, 4);
+}
diff --git a/libqpdf/qpdf/Pl_Base64.hh b/libqpdf/qpdf/Pl_Base64.hh
new file mode 100644
index 00000000..313bd2cb
--- /dev/null
+++ b/libqpdf/qpdf/Pl_Base64.hh
@@ -0,0 +1,30 @@
+#ifndef PL_BASE64_HH
+#define PL_BASE64_HH
+
+#include <qpdf/Pipeline.hh>
+
+class Pl_Base64: public Pipeline
+{
+  public:
+    enum action_e { a_encode, a_decode };
+    Pl_Base64(char const* identifier, Pipeline* next, action_e);
+    virtual ~Pl_Base64() = default;
+    virtual void write(unsigned char* buf, size_t len) override;
+    virtual void finish() override;
+
+  private:
+    void decode(unsigned char* buf, size_t len);
+    void encode(unsigned char* buf, size_t len);
+    void flush();
+    void flush_decode();
+    void flush_encode();
+    void reset();
+
+    action_e action;
+    unsigned char buf[4];
+    size_t pos;
+    bool end_of_data;
+    bool finished;
+};
+
+#endif // PL_BASE64_HH