解决方法
有一个avro_writer_memory()完全针对这种情况,它需要缓冲区指针和长度作为参数,并给出可用于常规写入功能的avro_writer_t.您可以在测试中找到它的用法,例如
this或
this.最小的例子将是这样的(将编码值输出到stderr,所以更好地重定向到某些文件,并在程序运行后检查)：
#include <avro.h> #include <stdio.h> #include <unistd.h> static const char json_schema[] = "{ \"type\": \"string\" }"; int main(void) { char buf[1024]; avro_writer_t writer; avro_schema_t schema; avro_value_iface_t* iface; avro_value_t val; size_t len; if (avro_schema_from_json_literal(json_schema,&schema) != 0) { printf("Failed to initialize schema\n"); goto out; } if ((writer = avro_writer_memory(buf,sizeof(buf))) == NULL) { printf("Failed to initialize writer\n"); goto out_schema; } if ((iface = avro_generic_class_from_schema(schema)) == NULL) { printf("Failed to get class from schema\n"); goto out_writer; } if (avro_generic_value_new(iface,&val) != 0) { printf("Failed to create new value\n"); goto out_iface; } if (avro_value_reset(&val) != 0) { printf("Failed to reset value\n"); goto out_val; } if (avro_value_set_string(&val,"some string wrapped by avro") != 0) { printf("Failed to set value string\n"); goto out_val; } if (avro_value_write(writer,&val) != 0) { printf("Failed to write value into the buffer\n"); goto out_val; } len = avro_writer_tell(writer); printf("got %lu bytes\n",(unsigned long)len); if (write(STDERR_FILENO,buf,len) != len) { printf("Failed to write to stderr,oops\n"); goto out_val; } out_val: avro_value_decref(&val); out_iface: avro_value_iface_decref(iface); out_writer: avro_writer_free(writer); out_schema: avro_schema_decref(schema); out: return 0; }
此外,还有一个avro_writer_memory_set_dest()允许设置新的缓冲区以供现有的作者使用.
