Fix libpinyin crash on ARMv7

Fix the alignment trap in get_unigram_frequency(). Fix also other
places where this same trap could happen (depending on compiler
and surrounding code).

The trap happened when the ARM GCC generated a SIMD instruction
(specifically VLDR) to load 32 bits in a single instruction, and
when the memory address was not aligned to 32 bits. VLDR traps if
the address is not aligned.

GCC generated the instruction because of the cast to uint32 from
the address. The fix is to allocate a uint32 variable in stack and
use memcpy to copy the data to that variable. This way we ensure
that appropriate instructions are generated.

**Links**

About the issue with GCC:
https://trust-in-soft.com/blog/2020/04/06/gcc-always-assumes-aligned-pointer-accesses/

How Linux does it:
https://elixir.bootlin.com/linux/v5.10.155/source/include/linux/unaligned/memmove.h#L13

ARM documentation:
https://documentation-service.arm.com/static/5f8dc043f86e16515cdbbc92?token=
    See 'A3.2.1 Unaligned data access'

1 files changed, 34 insertions, 0 deletions

diff --git a/src/include/memory_chunk.h b/src/include/memory_chunk.h
index c106dba..baa5679 100644
--- a/src/include/memory_chunk.h
+++ b/src/include/memory_chunk.h
@@ -290,6 +290,25 @@ public:
     }
 
     /**
+     * MemoryChunk::set_content:
+     * @offset: the offset in this MemoryChunk.
+     * @data: the data to be copied.
+     * @returns: whether the data is copied successfully.
+     *
+     * Data are written directly to the memory area in this MemoryChunk.
+     *
+     */
+    template <typename T>
+    bool set_content(size_t offset, T data){
+        const size_t len = sizeof(data);
+        size_t cursize = std_lite::max(size(), offset + len);
+        ensure_has_space(offset + len);
+        memmove(m_data_begin + offset, &data, len);
+        m_data_end = m_data_begin + cursize;
+        return true;
+    }
+
+    /**
      * MemoryChunk::append_content:
      * @data: the begin of the data to be copied.
      * @len: the length of the data to be copied.
@@ -357,6 +376,21 @@ public:
     }
 
     /**
+     * MemoryChunk::get_content:
+     * @offset: the offset in this MemoryChunk.
+     * @returns: the content
+     *
+     * Get the content in this MemoryChunk.
+     *
+     */
+    template <typename T>
+    T get_content(size_t offset) const {
+        T value;
+        memcpy(&value, m_data_begin + offset, sizeof(value));
+        return value;
+    }
+
+    /**
      * MemoryChunk::compact_memory:
      *
      * Compact memory, reduce the size.